The Technical Vault
By SOSCleanroom
KIMBLE 41A2502
Non-Heparinized
Blue Coded
1.1 mm ID
75 mm Length
USP Type III Glass
200 / Vial
2,400 / Case
KIMBLE 41A2502: selecting the correct plain capillary for packed cell volume testing
KIMBLE® 41A2502 is a blue-coded, non-heparinized micro-hematocrit capillary tube manufactured by DWK Life Sciences. It is intended for determining packed cell volume in properly prepared blood samples using a compatible microhematocrit centrifuge and reading system.
The tube is manufactured from 90-expansion soda-lime glass, with a published 1.1 mm inside diameter and 75 mm length. DWK identifies the glass material as conforming to USP Type III requirements.
This SKU is not heparin-treated. Its blue color coding distinguishes it from red-coded heparinized microhematocrit tubes. The distinction is important because the plain tube requires an appropriately anticoagulated specimen when clot prevention is necessary for the test.
Operations takeaway: Choose 41A2502 when the laboratory's approved method calls for a plain, non-heparinized 1.1 x 75 mm glass capillary. The standard manufacturer package contains 2,400 tubes. For untreated direct capillary blood specimens, the laboratory may need an appropriate heparinized variant instead.
Specifications (SKU controls for purchasing, SOPs, and receiving)
- Manufacturer: DWK Life Sciences
- Brand: KIMBLE® / historical KIMBLE CHASE
- Catalog Number: 41A2502
- Product Family: Micro-Hematocrit Capillary Tubes
- Configuration: Plain, non-heparinized
- Color Code: Blue
- Glass: Soda-lime
- Glass Expansion Category: 90-expansion soda-lime glass
- Glass-Material Classification: USP Type III, as identified by DWK
- Inside Diameter (ID): 1.1 mm
- Overall Tube Length: 75 mm
- Outside Diameter: Not specified in the reviewed current product record
- Wall Thickness: Not specified in the reviewed current product record
- Capillary Anticoagulant: None
- Sealing: Manufacturer describes flame sealing or sealing clay
- Inner Container: Plastic vial with reclosable snap-lock cap
- Inner Pack: 200 tubes per vial
- Vials per Case: 12
- Total Manufacturer Case: 2,400 tubes
- Primary Application: Hematocrit / packed cell volume determination
- Compatible Sample Context: Appropriately anticoagulated blood under a validated method
- Supplied Sterility: Not established by the reviewed DWK product record
Specification rule: The manufacturer's 1.1 mm dimension is the inside diameter, not the outside diameter. The 75 mm dimension is tube length. Do not replace either value with an estimated outer diameter, nominal blood volume, or unverified calibration marking.
Non-heparinized versus heparinized: why blue and red codes matter
DWK distinguishes its microhematocrit products using the following color designations: blue for non-heparinized and red for heparinized. The color identifies whether the capillary has the manufacturer's heparin anticoagulant treatment.
Non-heparinized capillaries are generally appropriate when blood has already been anticoagulated during collection, such as a properly prepared EDTA whole-blood sample. Heparinized capillaries are typically selected when a sample is collected directly from a skin puncture and does not have an anticoagulant already present.
| Feature |
Non-Heparinized |
Heparinized |
| Color code |
Blue |
Red |
| Heparin treatment |
None |
Present |
| Typical specimen |
Already anticoagulated blood |
Blood collected directly from an appropriate skin puncture |
| 2,400-count SKU |
41A2502 |
41B2501 |
| 1,200-count SKU |
40A502 |
40B501 |
Critical specimen-selection point: Blue-coded 41A2502 does not contain heparin and therefore does not independently prevent clotting. Use an appropriately anticoagulated specimen. Do not interchange blue and red capillaries without confirming the applicable testing procedure.
Microhematocrit and packed cell volume: what the test measures
Hematocrit represents the proportion of whole blood occupied by red blood cells. The manual microhematocrit method uses centrifugation to separate packed red blood cells from plasma and other cellular components.
After appropriate centrifugation, the tube generally contains a packed red cell layer, a thin buffy coat consisting primarily of white blood cells and platelets, and a plasma layer. The height of the packed red cell column is compared with the total measured blood column.
General measurement principle:
Hematocrit (%) = (Packed red cell column height ÷ Total blood column height) × 100
- Packed Red Cells: The compact red blood cell fraction after centrifugation.
- Buffy Coat: White blood cell and platelet layer; excluded from the red cell measurement.
- Plasma: The liquid fraction above the cellular layers.
- Total Blood Column: The method-defined total sample height used in calculating the percentage.
- Reported Value: The method-defined hematocrit or packed cell volume result.
The result may be affected by trapped plasma within the packed red cell layer, sample quality, centrifugation conditions, and errors in locating the interfaces between layers.
Measurement boundary: The tube does not measure hematocrit electronically or provide an automatic diagnostic result. Centrifugation, a compatible reading method, quality controls, and clinical interpretation are separate from the glass consumable.
90-expansion soda-lime glass and USP Type III material classification
DWK specifically identifies the KIMBLE microhematocrit tube family as manufactured from 90-expansion soda-lime glass conforming to USP Type III glass requirements. This is an important distinction from the borosilicate glass used in many other KIMBLE laboratory products.
USP Type III is a glass-material classification. It does not by itself certify that the finished capillary is sterile, individually calibrated, approved for every clinical application, or interchangeable with a borosilicate glass product.
- Standard Material: Soda-lime glass.
- Expansion Category: 90-expansion.
- Manufacturer-Listed Glass Category: USP Type III.
- Borosilicate: Described by DWK as available through special order, not the standard material for this SKU.
- Glass Composition: Do not substitute general borosilicate properties for soda-lime glass.
- Clinical Suitability: Requires the appropriate tube design, specimen handling, and method qualification.
- Finished-Product Certificate: No individual test certificate established by the reviewed SKU listing.
Material classification distinction: Do not describe 41A2502 as borosilicate 3.3, USP Type I, or ASTM E438 Type I Class A. The standard manufacturer designation for this product is soda-lime glass conforming to USP Type III requirements.
Review DWK's Glass Types & Properties Technical Guide
1.1 mm inside diameter and 75 mm length: equipment-fit considerations
The published 1.1 mm dimension is the inside diameter of the capillary tube, and 75 mm is its length. These measurements are important when selecting a tube for a laboratory's microhematocrit centrifuge and reading equipment.
The current manufacturer product listing does not specify the tube's outside diameter, glass wall thickness, exact sample volume, or dimensional tolerances for these parameters. Those values should not be calculated and published as manufacturer-certified specifications.
| Specification |
Value |
Selection significance |
| Inside diameter |
1.1 mm |
Internal sample column geometry |
| Tube length |
75 mm |
Centrifuge rotor and reader compatibility |
| Outside diameter |
Not specified |
Confirm if a particular holder has strict fit limits |
| Wall thickness |
Not specified |
Do not assume an unlisted glass wall dimension |
| Sample fill |
Method dependent |
Follow the approved hematocrit procedure |
Equipment compatibility checkpoint: Confirm the microhematocrit centrifuge rotor, capillary holder, and reader are appropriate for the actual 75 mm glass tube. Do not assume every rotor or automated reader accepts all capillaries sharing the same inside diameter.
Anticoagulated specimens: preventing clotting and preserving test integrity
Non-heparinized tubes are commonly used when a whole-blood specimen has already been collected in a suitable anticoagulant-containing container. Under such conditions, the capillary does not need to add a further heparin treatment.
The laboratory must verify the correct specimen type, anticoagulant, storage interval, mixing technique, and testing procedure. Poorly mixed or partially clotted blood can produce unreliable red cell packing and measurement results.
- Prior Anticoagulation: Verify that the specimen contains a method-appropriate anticoagulant.
- Specimen Mixing: Follow approved handling procedures before transferring blood into the capillary.
- Clotted Samples: Do not assume a non-heparinized capillary can restore validity to a clotted specimen.
- Collection Method: Differentiate previously anticoagulated venous blood from untreated direct capillary collection.
- Storage Conditions: Follow the method's time and temperature requirements.
- Sample Identification: Maintain traceability between the specimen and the capillary measurement.
Specimen qualification: Non-heparinized does not mean anticoagulation is unnecessary. It means no anticoagulant is included in the capillary itself. Selection must be consistent with the laboratory's specimen collection and testing method.
Capillary filling and end sealing: controlling leakage and sample loss
DWK notes that its microhematocrit capillaries may be sealed by flame or sealing clay. In routine hematocrit workflows, an approved sealing material is commonly used to close the required end of a blood-filled tube before centrifugation.
Sealing quality is important because a weak or incomplete seal can allow specimen leakage during centrifugation. The applicable laboratory method and centrifuge manufacturer's instructions determine how tubes are filled, sealed, and loaded.
- Capillary Filling: Follow the method-defined level and avoid trapped air.
- Outer Surface: Prevent blood contamination on the outside of the tube and clean as the SOP directs.
- Sealing Material: Use suitable clay or another approved compatible sealing method.
- Seal Quality: Check for gaps, irregular application, or inadequate retention.
- Pre-centrifuge Inspection: Reject visibly damaged, leaking, or improperly prepared tubes.
- Safe Handling: Avoid broken-glass injury and follow bloodborne-pathogen precautions.
Safety point: Although DWK describes flame sealing as a possible tube-sealing technique, do not use an open flame near blood specimens unless a specific validated laboratory procedure and safety assessment expressly permit it. Follow the institutional blood-sample sealing procedure.
Microhematocrit centrifugation: equipment compatibility and procedure controls
Microhematocrit determination uses high-speed centrifugation to pack the red blood cells into a measurable column. The capillary tube is one part of a larger system that includes a compatible rotor, suitable end seal, centrifugal force, centrifugation time, and hematocrit reading device.
The manufacturer listing for 41A2502 does not provide a universal centrifuge speed, centrifugal force, operating time, rotor specification, or validated clinical procedure. These requirements should be determined by the actual instrument and approved laboratory method.
- Confirm tube compatibility: Verify the rotor accepts the relevant glass capillary dimensions.
- Check the end seal: Inspect for a proper seal before loading.
- Load correctly: Follow the rotor manufacturer's orientation and loading instructions.
- Balance the centrifuge: Use the required balanced arrangement to reduce mechanical stress.
- Apply approved conditions: Use the laboratory's validated force, speed, and time.
- Observe safety controls: Keep the instrument closed and wait for complete rotor stoppage before accessing tubes.
- Inspect after centrifugation: Check for breakage, leakage, or unusable separation.
- Read as specified: Use the approved hematocrit reader and measurement procedure.
Operating limit: Do not publish a manufacturer-certified maximum RPM or relative centrifugal force for 41A2502 unless DWK provides a product-specific rating. Approved centrifugation parameters are determined by the instrument and test method.
Reading the hematocrit: red cell column, buffy coat, and plasma
After centrifugation, the red blood cell column is read relative to the entire sample column. The thin buffy coat between the packed cells and plasma should not be counted as packed red blood cells.
The laboratory should use a compatible calibrated or properly verified reading device and apply the method's rules for aligning the packed cell layer and total blood column.
| Layer |
Description |
Reading relevance |
| Packed red cells |
Compacted red blood cell fraction |
Used in the hematocrit numerator |
| Buffy coat |
Thin white blood cell and platelet layer |
Excluded from packed red cell height |
| Plasma |
Liquid fraction above the cells |
Part of the total original blood column |
Interpretation checkpoint: Including the buffy coat in the red cell measurement can bias the reported hematocrit. Always follow the reading method and laboratory quality-control requirements.
Common microhematocrit error sources and practical controls
The reliability of a manual hematocrit result depends on more than the capillary. Proper specimen handling, centrifugation, and measurement are necessary to limit avoidable errors.
| Potential error |
Control consideration |
| Clotted specimen |
Confirm prior anticoagulation and method-defined specimen acceptance |
| Improper mixing |
Use the laboratory's approved whole-blood mixing procedure |
| Inadequate end seal |
Check for complete, secure sealing before centrifugation |
| Insufficient centrifugation |
Follow validated instrument conditions for adequate cell packing |
| Trapped plasma |
Recognize method-related limitations and follow established reading rules |
| Buffy coat inclusion |
Exclude the buffy coat from red cell column height |
| Broken or leaking tube |
Reject compromised tests and follow biohazard cleanup procedures |
| Reading misalignment |
Use the appropriate reader and correct column alignment |
Manual hematocrit may differ from certain automated instrument calculations. Laboratories should use method-specific quality controls and acceptance criteria rather than treating the two measurement approaches as automatically identical.
Packaging: 200-capillary snap-lock vials and 2,400-tube manufacturer cases
DWK lists a quantity of 2,400 for catalog 41A2502. Manufacturer product-family information describes plastic vials with reclosable snap-lock caps, while established catalog and distributor specifications identify the standard inner pack as 200 tubes per vial.
This yields 12 vials per 2,400-tube case. The reclosable vials are packaging for the unused glass capillaries and are not sterile specimen containers.
- Manufacturer Case: 2,400 capillaries.
- Inner Pack: 200 capillaries.
- Inner Vial Count: 12 per case.
- Inner Container: Plastic vial.
- Vial Closure: Reclosable snap-lock cap.
- Smaller Selling Units: Confirm availability with SOSCleanroom before offering single vials for purchase.
BigCommerce purchasing checkpoint: Use 2,400 tubes per case as the default manufacturer sale quantity. The 200-count vial is an inner package; do not price it as a separately available retail unit unless SOSCleanroom has explicitly established that selling configuration.
KIMBLE microhematocrit family: product selection and case size comparison
DWK offers related 1.1 x 75 mm capillary products with different anticoagulant treatments and manufacturer quantities. The correct choice depends on specimen preparation and required case size.
| Catalog Number |
Treatment |
Color |
ID x Length |
Case Qty. |
| 41A2502 |
Non-heparinized |
Blue |
1.1 x 75 mm |
2,400 |
| 40A502 |
Non-heparinized |
Blue |
1.1 x 75 mm |
1,200 |
| 41B2501 |
Heparinized |
Red |
1.1 x 75 mm |
2,400 |
| 40B501 |
Heparinized |
Red |
1.1 x 75 mm |
1,200 |
All four catalog numbers refer to separate manufacturer products. Case quantity and anticoagulant status should both be verified before substituting one SKU for another.
Substitution warning: A 1,200-count plain tube may be a packaging alternative to a 2,400-count plain tube, but a red-coded heparinized tube is a different specimen-contact configuration. A laboratory must authorize any anticoagulant-treatment substitution.
Sterility, cleanroom suitability, and clinical qualification boundaries
The reviewed DWK product listing identifies material, dimensions, anticoagulant configuration, color code, and package quantity. It does not explicitly establish that 41A2502 is supplied sterile, has a validated sterility assurance level, or is individually certified to a particular ISO cleanroom cleanliness classification.
USP Type III refers to the glass material and does not replace qualification of the complete tube for a laboratory's intended clinical or research use. Diagnostic laboratories must follow their applicable regulatory requirements and established testing procedures.
- Supplied Sterility: Not established by the reviewed SKU record.
- Sterility Assurance Level: Not specified.
- ISO Cleanroom Rating: No product-specific classification identified.
- Individual Calibration: No tube-specific measurement calibration established.
- Regulatory Device Status: Obtain manufacturer documentation if a specific registration or authorization is required.
- Reuse or Reprocessing: No validated reuse protocol established in the reviewed product information.
- Clinical Performance: Depends on the complete approved measurement method and quality controls.
Qualification boundary: Do not advertise 41A2502 as sterile, FDA-cleared, individually calibrated, or cleanroom certified without current documentation establishing the specific claim.
Bloodborne-pathogen precautions, broken glass, and sharps disposal
A blood-filled hematocrit capillary combines the potential hazards of a biological specimen and fragile glass. Used tubes, broken fragments, and contaminated sealing materials should be handled according to institutional biosafety and regulated waste procedures.
The plastic snap-lock vial is intended to store and protect unused capillaries. It should not automatically be treated as a compliant disposal container for used blood-contaminated sharps.
- Protective Equipment: Use required laboratory gloves, eye protection, and other PPE.
- Blood Handling: Follow universal or standard precautions required by the facility.
- Glass Inspection: Reject cracked, chipped, or otherwise damaged tubes.
- Centrifuge Safety: Use appropriate tube supports and approved operating procedures.
- Breakage Response: Apply the facility's procedure for handling contaminated broken glass.
- Sharps Disposal: Discard used and broken contaminated capillaries into approved puncture-resistant sharps containers.
- No Assumed Reuse: Do not reuse a blood-contaminated capillary unless an explicitly validated process applies.
Safety reminder: Never pick up contaminated capillary fragments with bare hands. Follow approved broken-glass and biological spill procedures, and do not dispose of contaminated glass in ordinary laboratory trash.
Storage and handling of unused microhematocrit capillaries
The manufacturer packages unused glass capillaries in plastic vials with reclosable snap-lock caps to help maintain cleanliness during storage. Good handling practices reduce the likelihood of broken tubes, contamination, or accidental mixing of different capillary types.
- Keep Vials Closed: Reclose the snap-lock cap after dispensing the required tubes.
- Protect From Impact: Avoid crushing, dropping, or shaking the capillary vial unnecessarily.
- Keep Dry and Clean: Protect unused tubes from environmental contamination under the laboratory's procedure.
- Separate Color Codes: Do not mix blue non-heparinized and red heparinized tubes.
- Maintain Labels: Retain manufacturer SKU, package identification, and any applicable lot information.
- Check Before Use: Inspect individual capillaries before introducing a blood sample.
The current manufacturer listing does not specify a product shelf life, validated expiration period, or special storage temperature for the 41A2502 finished tube. Follow applicable packaging labels and obtain current manufacturer clarification when storage limits are required by the facility.
Receiving, packaging, and inspection checklist
Receiving inspection should confirm the exact 41A2502 non-heparinized configuration, blue color code, and intended case packaging. This is especially important where both red and blue microhematocrit products are held in laboratory inventory.
- Verify Catalog Number: Match 41A2502 to the purchase order and receiving documents.
- Verify Anticoagulant Configuration: Confirm the non-heparinized/plain designation.
- Check Color Code: Verify blue rather than red.
- Confirm Dimensions: Check the published 1.1 mm ID and 75 mm length.
- Confirm Case Quantity: Verify 2,400 tubes.
- Check Inner Packaging: Verify the expected 200-tube vials and 12-vial configuration.
- Inspect Packaging: Look for broken vials, open caps, contamination, or shipping damage.
- Inspect Representative Tubes: Check for breakage, chipped ends, fragments, or irregular glass.
- Check Labeling: Retain SKU and lot information according to the quality procedure.
- Record Disposition: Release, reject, or quarantine the shipment according to institutional receiving requirements.
Receiving checkpoint: Do not substitute the 41B2501 red-coded heparinized tube for the 41A2502 blue-coded non-heparinized tube solely because both are 1.1 x 75 mm and packaged 2,400 per case.
Technical FAQs
Is KIMBLE 41A2502 heparinized?
No. It is a plain, non-heparinized microhematocrit tube identified by blue color coding.
Why are these tubes blue coded?
DWK uses blue to identify the non-heparinized capillary configuration. Heparinized tubes are red coded.
What type of blood is appropriate for a non-heparinized capillary?
They are generally selected for blood that has already been anticoagulated, such as appropriately prepared EDTA whole blood. Follow the laboratory's specimen requirements.
Can I use a non-heparinized tube to collect untreated blood directly from a finger puncture?
An untreated direct capillary specimen may clot in a plain tube. An appropriate heparinized capillary is generally selected for that collection approach under the approved method.
What are the tube dimensions?
DWK specifies a 1.1 mm inside diameter and a 75 mm overall length. The current listing does not provide an outside diameter or wall thickness.
Are these borosilicate glass tubes?
No. The standard 41A2502 configuration is made from 90-expansion soda-lime glass. DWK identifies borosilicate as a separate special-order possibility.
What does USP Type III mean?
It is a manufacturer-stated glass material classification. It does not independently certify the completed capillary as sterile, individually calibrated, or appropriate for every diagnostic method.
How many tubes are in a vial?
The standard 41A2502 inner vial contains 200 tubes, and a case contains 12 vials.
How many capillaries come in a manufacturer case?
DWK lists 2,400 capillary tubes for catalog 41A2502.
What is the difference between 41A2502 and 40A502?
Both are blue-coded non-heparinized 1.1 x 75 mm microhematocrit tubes. Their standard manufacturer case quantities differ: 2,400 for 41A2502 and 1,200 for 40A502.
What is the heparinized alternative?
KIMBLE 41B2501 is a red-coded heparinized 1.1 x 75 mm tube supplied in a 2,400-count case. It is a different anticoagulant configuration.
Can the tubes be sealed using clay?
Yes. DWK identifies sealing clay as an available end-sealing method. The actual material and procedure should be approved for the laboratory's test.
Does the capillary include sealing clay or a hematocrit reader?
No. The product is the glass capillary consumable. Sealing materials, centrifuges, and readers are separate equipment or supplies.
Are the capillaries supplied sterile?
A supplied-sterile designation was not established by the reviewed DWK listing. The snap-lock packaging is described as protecting cleanliness, not as a sterile barrier.
Is the tube compatible with every microhematocrit centrifuge?
No universal compatibility is established. Confirm the centrifuge rotor and reading system's approved tube dimensions and operating requirements.
Can used blood-filled capillaries be disposed of in ordinary trash?
No. Used or broken blood-contaminated glass capillaries should be handled according to the facility's sharps and biohazard disposal procedures.
Why purchase KIMBLE microhematocrit tubes from SOSCleanroom
- Exact SKU identification: SOSCleanroom helps laboratories distinguish non-heparinized and heparinized capillary configurations.
- Accurate package selection: Confirm the correct 1,200-count or 2,400-count manufacturer case before ordering.
- Glass and dimension verification: Request assistance confirming the soda-lime glass specification and the required 1.1 x 75 mm geometry.
- Laboratory consumable sourcing: Source specialty capillaries and related laboratory supplies through SOSCleanroom.
- Manufacturer documentation: Ask for help requesting available product data and material specifications.
- Responsive support: Contact SOSCleanroom for formal quotations, availability, and product-selection assistance.
Manufacturer documentation and technical references
-
DWK Glass Types & Properties:
Review Manufacturer Glass Material Information
— general distinctions between laboratory glass compositions, material classifications, and relevant properties.
-
DWK Care & Maintenance of Laboratory Glassware:
Review Manufacturer Glassware Handling Guidance
— general information about inspecting and safely handling laboratory glass.
-
Clinical Testing Procedure: Refer to the laboratory's approved microhematocrit or packed cell volume procedure and the applicable centrifuge and hematocrit reader instructions for specimen handling, sealing, centrifugation, and result interpretation.
-
Product-Specific Documentation: Contact SOSCleanroom for assistance requesting current DWK specifications or further information about catalog number 41A2502.
The current DWK listing verifies the non-heparinized, blue-coded product identity; 1.1 mm ID; 75 mm length; 90-expansion soda-lime glass; USP Type III material description; and 2,400-tube quantity. The 200-tube vial configuration is corroborated by established distributor catalog records.
Technical explanations of specimen anticoagulation and hematocrit interpretation are general laboratory-method guidance, not product-specific clinical performance claims. Follow the approved testing method for all clinical or regulated use.
If you have any questions please email us at Sales@SOSsupply.com or give us a call at (214) 340-8574.
For additional product guidance, use the SOSCleanroom AI ChatBot or contact our team for manufacturer documentation assistance.
Technical insight: The most important selection distinction for 41A2502 is the absence of heparin. Blue-coded plain microhematocrit tubes should be matched to appropriately anticoagulated specimens, compatible centrifuges, method-defined sealing procedures, and suitable packed cell volume reading methods.
Last updated: October 28, 2026
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