16 mm Test Tube Stoppers — LDPE, Red, 1000/Bag (300-2916-R20)
These red low-density polyethylene (LDPE) stopper caps are engineered for 16 mm OD test tubes — including standard 16 × 100 mm formats — used in clinical chemistry, serology, microbiology culture, and specimen archiving workflows. The plug-in friction-fit design relies on LDPE's characteristic flex modulus to provide consistent compression and spring-back across repeated insertion and removal cycles, maintaining a reliable seal without adhesives or secondary closures. Supplied non-sterile in 1000/Bag, they offer a cost-effective solution for high-throughput tube management at the bench or in clinical sample-processing areas.
Technical Specifications
| Specification | Value |
|---|---|
| Part Number (MPN) | 300-2916-R20 |
| Tube OD | 16 mm |
| Compatible Tube Format | 16 × 100 mm |
| Cap Style | Stopper — plug-in friction fit |
| Material | Low-Density Polyethylene (LDPE) |
| Color | Red |
| Temperature Range | -20°C to +60°C |
| Sterility | Non-Sterile |
| Pack Size | 1000/Bag |
| BPA / Phthalates | BPA-free; no phthalate plasticizers |
| Country of Origin | USA |
Applications
- Clinical specimen archiving: Seals serum, plasma, and whole-blood tubes during refrigerated or frozen long-term storage, preventing evaporation and cross-contamination.
- Microbiology culture tube capping: Retains flexibility at 37°C incubation temperatures, providing a stable closure for TSB, BHI, LB broth, and similar liquid media tubes.
- Cell culture and virus propagation: Stopper-style fit allows controlled gas exchange while blocking environmental contamination during suspension culture workflows.
- Clinical tube color routing: Red mirrors the CLSI H3 red-top serum convention, supporting color-coded specimen-type identification and routing without relabeling.
- Pneumatic tube transport: LDPE flexibility absorbs acceleration forces encountered in clinical pneumatic transport systems without compromising the friction-fit seal.
- Research reagent and buffer tubes: Stopper seals reusable glass and polystyrene tubes between uses during reagent preparation and stock solution archiving.
- Hematology and coagulation: Color-coded stoppers support anticoagulant tube designation for EDTA and citrate tube formats.
Chemical Resistance
| Reagent / Condition | Compatibility |
|---|---|
| Aqueous buffers and saline | Excellent |
| Serum and plasma | Excellent — inert, no leaching |
| Broth media (TSB, BHI, LB) | Excellent |
| Dilute acids and bases | Good |
| Ethanol and isopropanol | Good — short-term contact; avoid prolonged immersion |
| Chlorinated solvents (chloroform, DCM) | Not recommended |
| Aromatic solvents (toluene, xylene) | Not recommended |
| Frozen storage (-20°C) | Excellent — LDPE retains flexibility; no brittle failure |
| Incubation (up to +60°C) | Excellent — seal engagement maintained |
Quality & Procurement
Made in USA, these Caplugs® Evergreen stoppers are produced from BPA-free, phthalate-free LDPE resin under ISO 9001 quality management, ensuring lot-to-lot dimensional consistency critical for reliable friction-fit retention across 16 mm tube formats. LabSupplies.com is an authorized Caplugs® Evergreen dealer shipping from USA inventory, with tiered volume pricing available for clinical labs, hospitals, and research institutions managing high-throughput tube workflows. Always validate fit against your specific tube brand before committing to bulk purchase, as 16 mm OD tubes can vary in opening diameter depending on wall thickness — contact us to request a sample.
Frequently Asked Questions
Are these stoppers compatible with all 16 mm test tubes?
They are designed for standard 16 mm OD tubes, including the common 16 × 100 mm format. Because wall thickness varies by manufacturer, the actual opening diameter can differ slightly between tube brands. We recommend validating fit with your specific tubes — contact LabSupplies.com to request a sample before placing a bulk order.
Can these stoppers be used for frozen specimen storage?
Yes. LDPE retains its characteristic flexibility down to -20°C, so the stopper will not become brittle or crack during removal from frozen archives — a common failure mode with more rigid cap materials.
Why is the red color significant in a clinical setting?
Red mirrors the CLSI H3 red-top serum tube convention, making these stoppers a natural fit for color-coded specimen routing that designates serum-containing or no-additive tubes. Staff can identify tube type by color at a glance without retraining.
Are these stoppers sterile, and can they be autoclaved?
These stoppers are supplied non-sterile. LDPE is not autoclavable — sustained exposure to steam autoclave temperatures (121°C) exceeds the material's safe temperature range of -20°C to +60°C and will deform the stopper. For sterile applications, treat with appropriate cold sterilization methods and validate before use.