16 mm Test Tube Stoppers — LDPE, Natural, 1000/Bag (300-2916-020)
These natural low-density polyethylene (LDPE) stoppers provide a reliable plug-in friction fit for standard 16 mm OD test tubes — including 16 × 100 mm formats — used across clinical chemistry, serology, microbiology culture, and specimen archiving workflows. Supplied non-sterile in 1000/Bag bulk packaging, they are the all-purpose default closure for high-throughput 16 mm tube programs. LDPE's inherent flex modulus delivers the compression and spring-back needed for repeated insertion and removal cycles while remaining inert to serum, plasma, broth media, and aqueous buffers.
Technical Specifications
| Specification | Value |
|---|---|
| Part Number (MPN) | 300-2916-020 |
| Tube OD | 16 mm |
| Compatible Tube Format | 16 × 100 mm |
| Cap Style | Stopper — plug-in friction fit |
| Material | Low-Density Polyethylene (LDPE) |
| Color | Natural |
| 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
- Microbiology culture tube capping: Seals TSB, BHI, LB broth, and other culture media tubes during incubation; LDPE retains flexibility at 37°C for repeated stopper access.
- Specimen tube archiving: Prevents evaporation from serum, plasma, and blood tubes during refrigerated or frozen storage down to -20°C.
- Clinical chemistry and serology: Provides an inert pre-analysis and post-analysis closure compatible with standard 16 mm chemistry tube formats; LDPE does not leach into specimen matrices.
- Cell culture: Caps suspension culture and virus propagation tubes while maintaining stopper flexibility across incubation temperature cycles.
- Pneumatic tube transport: LDPE flex retention survives the acceleration forces of clinical pneumatic transport systems without stopper ejection.
- Research reagent and buffer storage: Seals reusable glass and polystyrene tubes between uses; natural color accommodates any labeling method or tube-type workflow.
- Hematology and coagulation tube handling: Compatible with EDTA and citrate anticoagulant tube formats in downstream processing steps.
Chemical Resistance
| Reagent / Condition | Compatibility |
|---|---|
| Aqueous buffers / water | Excellent |
| Serum / plasma / whole blood | Excellent |
| Urine / urine matrices | Excellent |
| Broth media (TSB, BHI, LB) | Excellent |
| Dilute acids and bases | Good |
| Ethanol (<70%) | Good — short-term contact |
| Acetone / chlorinated solvents | Not recommended |
| Aromatic solvents (toluene, xylene) | Not recommended |
Quality & Procurement
Made in USA, these Caplugs® Evergreen stoppers are produced under ISO 9001 quality management from BPA-free, phthalate-free LDPE resin. The natural color and LDPE formulation are validated for clinical specimen contact applications. 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-volume tube programs. Always validate stopper fit against your specific tube brand before bulk purchase, as wall thickness can affect opening diameter within the 16 mm OD class — contact us to request a free sample.
Frequently Asked Questions
Will these stoppers fit any 16 mm test tube?
They are designed for standard 16 mm OD tubes, including the common 16 × 100 mm format. Because tube wall thickness varies by manufacturer, the actual opening diameter can differ slightly between brands. Validating fit with your specific tube before placing a bulk order is strongly recommended — contact LabSupplies.com to request a sample.
Can these stoppers be used for frozen specimen storage?
Yes. LDPE retains its flexibility down to -20°C, so the friction fit remains intact and stoppers can be removed without brittle cracking even after extended frozen archive storage.
Are these stoppers autoclavable?
No. LDPE is not rated for autoclave sterilization. The working temperature range is -20°C to +60°C. For applications requiring sterile closures, pre-sterilized options or an alternative material should be considered.
Why are the stoppers natural (translucent) rather than colored?
Natural LDPE is the universal default for 16 mm tube workflows — it is compatible with every labeling method (pen, label, barcode) and imposes no color-coding convention on mixed tube programs. Color-coded variants are available separately for labs using stopper color to designate specimen type or anticoagulant format.