Green LDPE Stopper Caps for 9 mm Test Tubes — Friction-Fit Tube Closures, 1000/Bag
These green Low-Density Polyethylene (LDPE) stopper caps are designed to plug into the opening of 9 mm OD test tubes and culture tubes, creating a positive friction-fit seal that prevents evaporation, contamination, and spillage during incubation, refrigerated storage, frozen archiving, and specimen transport. Supplied non-sterile in convenient 1000/Bag quantities, the Caplugs® Evergreen line identified by part number 300-2909-G20 delivers reliable, high-volume tube closure for clinical, microbiological, and research workflows. The green color supports color-coded tube routing, enabling rapid visual differentiation of specimen types or processing batches across the lab bench and storage rack.
Technical Specifications
| Specification | Value |
|---|---|
| Part Number (MPN) | 300-2909-G20 |
| Tube OD | 9 mm |
| Cap Style | Stopper — plug-in friction fit |
| Material | Low-Density Polyethylene (LDPE) |
| Color | Green |
| 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 — sealing TSB, BHI broth, and other liquid culture media tubes during incubation to prevent airborne contamination
- Specimen tube archiving — closing serum, plasma, and urine tubes for refrigerated or frozen storage through freeze-thaw cycles down to -20°C
- Clinical chemistry sample tubes — friction-fit seal minimizes evaporation of sample matrix during batched processing
- Pneumatic tube transport — retained stopper prevents spillage and cross-contamination during intra-facility specimen transit
- Color-coded tube management — green stoppers distinguish designated specimen types, patient cohort groups, or processing batches at a glance in high-throughput rack workflows
Chemical Resistance
| Reagent / Condition | Compatibility |
|---|---|
| Aqueous buffers and saline | Excellent |
| Urine, serum, plasma matrices | Excellent |
| Broth culture media (TSB, BHI) | Excellent |
| Dilute acids and bases | Good |
| Alcohols (short-term contact) | Good |
| Acetone / aromatic solvents | Not recommended |
| Chlorinated solvents | Not recommended |
Quality & Procurement
Made in USA, these Caplugs® Evergreen stopper caps are manufactured from BPA-free, phthalate-free LDPE resin formulated for low extractables into sensitive specimen matrices. The inherent flexibility of low-density polyethylene is essential for stopper-format closures — LDPE's flex modulus allows the plug to compress on insertion and recover against the tube inner wall, maintaining a secure friction-fit seal across the full -20°C to +60°C operating range without hardening or cracking at frozen storage temperatures. LabSupplies.com is an authorized Caplugs® Evergreen dealer and ships from USA inventory, with tiered volume pricing available for high-throughput laboratories, hospitals, and institutional procurement programs.
Frequently Asked Questions
Why are these stoppers made from LDPE rather than polypropylene or polystyrene?
The stopper-plug format requires a material that can compress under insertion force and elastically recover to grip the tube's inner wall by friction. LDPE's low flex modulus provides exactly this behavior. Rigid materials such as polypropylene, polystyrene, and HDPE lack sufficient flexibility for stopper-style closures and would crack or fail to retain against the tube wall.
Will these stoppers stay in place during freeze-thaw cycling?
Yes. LDPE retains its flexibility down to -20°C, so the stopper does not harden or lose its friction-fit engagement during frozen archiving or repeated freeze-thaw cycles. The stated operating range for these caps is -20°C to +60°C.
Are these stopper caps sterile?
No — they are supplied non-sterile in 1000/Bag bulk packaging. For applications requiring sterile closures, evaluate whether your workflow permits pre-use decontamination, or contact LabSupplies.com to inquire about sterile alternatives within the Caplugs® Evergreen range.
What tube dimensions are compatible with the 300-2909-G20 stopper?
These stoppers are designed for standard disposable test tubes and culture tubes with a 9 mm outer diameter, including common 9 × 70 mm culture tube formats. If your tubes differ in OD, Caplugs® Evergreen offers stopper caps in additional sizes — confirm your tube OD before ordering.