Caplugs® Evergreen
Test Tube Stoppers, LDPE, Natural — 300-2916-020 | 1000/Bag | Caplugs® Evergreen
Test Tube Stoppers, LDPE, Natural — 300-2916-020 | 1000/Bag | Caplugs® Evergreen
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Test Tube Stopper Caps for 16 mm Test Tubes, LDPE, Natural — 300-2916-020 | 1000/Bag
| Quick Reference — 300-2916-020 | |
|---|---|
| Tube OD | 16 mm |
| Cap Type | Stopper (plug-in friction fit) |
| Material | Low-Density Polyethylene (LDPE) |
| Color | Natural |
| Tube Types | 16 × 100 mm |
| Temp Range | -20°C to +60°C (LDPE flex range) |
| Sterility | Non-Sterile |
| Pack Size | 1000 / Bag |
| Price | $66.96 / Bag ($0.0670 / stopper) |
Technical Narrative
The Caplugs® Evergreen is a natural LDPE stopper cap for 16 mm OD test tubes — designed for 16 mm OD test tubes used in clinical chemistry, serology, and large-format culture tube workflows. The 16 mm stopper serves large-format clinical chemistry, serology, and culture tube workflows. Natural LDPE stoppers are the all-purpose default for 16 mm tubes, compatible with any labeling method and suitable for universal tube workflows.
LDPE's low-density flex modulus provides the compression and spring-back required for friction-fit stopper retention across repeated insertion/removal cycles — the property that makes LDPE the only appropriate material for stopper-style tube caps. LDPE retains flexibility from -20°C through 60°C, preventing brittle failure during frozen archive stopper removal and maintaining seal engagement during incubation. Chemical inertness to serum, plasma, broth media, and aqueous buffers ensures no leaching into tube contents.
At $66.96 per 1000/Bag — $0.0670 per stopper. Also available: 300-2916-R20 (Red 16 mm, $66.96); 300-2917-B2N (Blue 17 mm, $53.19).
Technical Specifications — Caplugs® Evergreen
| Specification | Value |
|---|---|
| Part Number | |
| Caplugs Item # | 3002916020E1 |
| Tube OD | 16 mm |
| Cap Style | Stopper — plug-in friction fit |
| Material | Low-Density Polyethylene (LDPE) |
| Color | Natural |
| Tube Compat. | 16 × 100 mm |
| Temp Range | -20°C to +60°C |
| Sterility | Non-Sterile |
| Pack Size | 1000 / Bag |
| BPA/Phthalate | BPA-free; no phthalate plasticizers |
| Country of Origin | Made in U.S.A. (California) |
Test Tube Stopper Application Compatibility — 16 mm
The 16 mm natural stopper fits standard 16 mm OD tubes for these workflows:
| Application | Specimen / Use | Notes |
|---|---|---|
| Culture tube capping | Microbiology culture tubes, TSB, BHI, LB broth | LDPE stopper seals tube during incubation; flex retained at 37°C |
| Specimen tube archiving | Serum, plasma, blood in refrigerated/frozen storage | Prevents evaporation during extended cold storage |
| Clinical tube color routing | CLSI-convention color stoppers for specimen-type ID | Color stop mirrors vacuum tube top-color conventions |
| Cell culture tube capping | Suspension culture, virus propagation | Stopper allows gas exchange while preventing contamination |
| Pneumatic tube transport | Sample tube transport in clinical systems | LDPE flex retention survives transport acceleration forces |
| Chemistry tube sealing | Pre-analysis sample tube closure | LDPE inert to serum/plasma; no leaching into specimen |
| Research reagent tubes | Buffer, reagent, stock solution tube archiving | Stopper seals reusable glass and PS tubes between uses |
| Hematology / coagulation | EDTA, citrate anticoagulant tube formats | Color-coded stoppers for anticoagulant tube designation |
Always validate stopper fit with your specific tube brand — 16 mm OD tubes vary in opening diameter by wall thickness. Request a free sample before bulk purchase.
Chemical Resistance — Low-Density Polyethylene (LDPE)
LDPE provides flexibility for friction-fit stopper retention and inertness to clinical specimen matrices.
| Reagent / Condition | Compatibility |
|---|---|
| Aqueous buffers / water | ✓ Excellent |
| Urine / serum / plasma | ✓ Excellent |
| Cell culture media | ✓ Excellent |
| Dilute acids (<10%) | ✓ Good |
| Dilute alkalies (pH <12) | ✓ Good |
| Short-chain alcohols (brief) | ✓ Good |
| DMSO (≤10%) | ✓ Good — brief contact |
| Autoclave (121°C) | ✗ Not compatible |
| Storage at -20°C | ✓ Suitable — LDPE retains flexibility |
Laboratory Applications
The serves microbiology culture tube programs, clinical chemistry and hematology tube archiving, and any laboratory requiring friction-fit sealed closure on 16 mm OD test tubes.
U.S. Manufacturing, Quality & Institutional Procurement
Every Caplugs® Evergreen lot is precision-molded at our California manufacturing facility and subject to rigorous dimensional inspection and material purity verification. We supply reference laboratories, hospital systems, and federal procurement offices under institutional pricing programs with blanket-order support and same-day shipping. Request a free sample below to validate fit before committing to volume.
Frequently Asked Questions — Caplugs® Evergreen
What tube formats use 16 mm OD and fit the stopper?
The fits 16 mm outer diameter test tubes, including: 16 × 100 mm, 16 × 125 mm, and 16 × 150 mm glass and PS test tubes, large clinical chemistry and serology tubes. Always validate fit with a sample before bulk purchase — opening diameter varies within the 16 mm OD range by wall thickness.
Is there a colored stopper available for 16 mm tubes?
Red (300-2916-R20) is available for 16 mm tubes at the same $66.96/1000 price. Choose Natural for universal use with any labeling system; choose Red when serum-specimen visual routing is a workflow requirement.
Why is LDPE used for stopper caps rather than PP or PS?
Stopper-style caps work by friction fit — the plug must compress under insertion and spring back against the tube inner wall. PP and PS are too rigid for this and crack under repeated insertion/removal cycles. LDPE's low-density flex allows thousands of insertion cycles without fracture, retains flexibility at -20°C to prevent brittle failure, and provides chemical inertness to clinical specimen matrices.
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