Caplugs® Evergreen
Test Tube Stoppers, LDPE, Natural — 300-2911-020 | 1000/Bag | Caplugs® Evergreen
Test Tube Stoppers, LDPE, Natural — 300-2911-020 | 1000/Bag | Caplugs® Evergreen
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Test Tube Stopper Caps for 11 mm Test Tubes, LDPE, Natural — 300-2911-020 | 1000/Bag
| Quick Reference — 300-2911-020 | |
|---|---|
| Tube OD | 11 mm |
| Cap Type | Stopper (plug-in friction fit) |
| Material | Low-Density Polyethylene (LDPE) |
| Color | Natural |
| Tube Types | 11 mm OD glass culture tubes |
| Flexibility | ✓ LDPE — flexible fit retained -20°C to +60°C |
| Sterility | Non-Sterile |
| Pack Size | 1000 / Bag |
| Price | $48.09 / Bag ($0.0481 / stopper) |
Technical Narrative
The Caplugs® Evergreen is a natural LDPE stopper cap for 11 mm OD test tubes — a plug-in friction-fit closure designed for 11 mm OD test tubes and culture tubes used in hematology, microbiology, and clinical sample prep workflows. The 11 mm size covers hematology, microbiology culture, and clinical sample prep tube workflows. Natural LDPE stoppers are the all-purpose default, compatible with any labeling method and suitable for universal tube workflows where color routing is handled by secondary barcode or label identification.
LDPE's low-density flex modulus allows the stopper plug to compress under insertion and spring back against the tube inner wall, providing retained friction-fit closure without the brittleness of rigid materials at the repeat insertion/removal cycles of clinical and research tube workflows. LDPE retains this flexibility from -20°C frozen archive through 60°C incubation — maintaining stopper retention through freeze-thaw cycles and incubation without hardening or losing friction-fit engagement. LDPE is chemically inert to urine, serum, plasma, broth media, and standard aqueous buffers — no leaching into tube contents during storage.
At $48.09 per 1000/Bag — $0.0481 per stopper — the delivers 11 mm natural tube closure at per-stopper economics for high-volume programs. Also available in this size: 300-2910-020 (Natural 10 mm ($44.43)); 300-2912-G20 (Green 12 mm ($44.13)).
Technical Specifications — Caplugs® Evergreen
| Specification | Value |
|---|---|
| Part Number | |
| Caplugs Item # | 3002911020E1 |
| Tube OD | 11 mm |
| Cap Style | Stopper — plug-in friction fit |
| Material | Low-Density Polyethylene (LDPE) |
| Color | Natural |
| Tube Compat. | 11 mm OD glass culture tubes |
| 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 —
The 11 mm natural LDPE stopper cap is designed for 11 mm OD test tubes and culture tubes used in hematology, microbiology, and clinical sample prep workflows. Compatible workflows:
| Application | Tube / Specimen Type | Notes |
|---|---|---|
| Culture tube capping | Microbiology culture tubes, TSB, BHI, LB broth | LDPE stopper seals tube during incubation; flexible fit retained at 37°C |
| Specimen tube archiving | Serum, plasma, urine in refrigerated/frozen storage | Stopper prevents evaporation during extended cold storage |
| Chemistry tube sealing | Clinical chemistry sample tubes pre-analysis | LDPE inert to serum/plasma matrix; no leaching into specimen |
| Cell culture tube capping | Suspension cell culture, virus propagation | Stopper allows gas exchange while preventing contamination |
| Pneumatic tube transport | Sample tube transport in clinical tube systems | LDPE flex retention survives transport acceleration forces |
| Color-coded batch routing | Visual specimen-type or priority designation | Color-stop tubes differentiated visually in loading racks |
| Research reagent tube caps | Buffer, reagent, stock solution tube closure | Stopper seals reusable glass and PS tubes between uses |
| Environmental sample tubes | Water, soil, field collection tubes | LDPE chemical inertness to aqueous environmental matrices |
Always validate stopper fit with your specific tube brand before bulk purchase — 11 mm OD tubes vary in opening diameter by wall thickness. Request a free sample to confirm friction-fit retention before volume commitment.
Chemical Resistance — Low-Density Polyethylene (LDPE)
LDPE provides the flexibility essential for stopper-format tube caps and broad chemical inertness to standard laboratory 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 |
| Concentrated organic solvents | ✗ Not recommended |
| Autoclave (121°C) | ✗ Not compatible — LDPE softens |
| Storage at -20°C | ✓ Suitable — LDPE retains flexibility |
Laboratory Applications
The serves clinical and research microbiology programs capping culture tubes during incubation; clinical chemistry and hematology labs archiving specimen tubes; research labs capping buffer and reagent stock tubes; cell culture programs requiring sealed tube incubation; and any laboratory workflow requiring friction-fit closure on 11 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 stopper fit with your tube brand before committing to volume.
Frequently Asked Questions — Caplugs® Evergreen
What test tube formats use 11 mm OD and fit the stopper?
The fits 11 mm outer diameter test tubes. Compatible formats include: 11 mm OD glass culture tubes, hematology prep tubes, and clinical laboratory sample prep tubes in the 11 mm format. Always validate stopper-to-tube fit with a sample set before bulk purchase — tube opening diameter varies within the 11 mm OD range depending on glass or plastic wall thickness. Request a free sample to confirm friction-fit retention before committing to volume.
Is there a colored stopper available for 11 mm tubes?
Natural is the only color available for 11 mm tube stoppers in the current Caplugs® Evergreen range. For color-coded routing in 11 mm tube workflows, Natural stoppers with secondary color-coded adhesive labels are the standard alternative. Choose Natural for universal use with any labeling system; choose a colored stopper when visual color-coded batch routing in the tube rack is a workflow requirement.
Why is LDPE specified for test tube stopper caps rather than PP or PS?
Stopper-style caps require a material with sufficient flex modulus to compress under insertion and spring back for friction retention — without fracturing under repeated use. PP and PS are too rigid and crack under the repeated insertion/removal forces of high-volume tube workflows. LDPE's low-density flex allows thousands of insertion/removal cycles without fracture, retains flexibility at -20°C to prevent brittle failure during frozen archive stopper removal, and provides chemical inertness to clinical specimen matrices (urine, serum, plasma, broth).
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