Test Tube Stoppers for 9 mm OD Tubes — LDPE, Natural, 1000/Bag (300-2909-020)
These natural Low-Density Polyethylene (LDPE) stopper caps are designed to close standard small test tubes and culture tubes with a 9 mm outer diameter using a plug-in friction fit that seats against the inner tube wall without threading or snap-over engagement. Supplied non-sterile in a convenient 1000/Bag pack, part number 300-2909-020 is well suited to high-volume tube capping programs in clinical labs, microbiology, and research settings. LDPE's inherent flexibility allows the stopper plug to compress on insertion and recover to maintain a positive friction-fit seal through refrigerated storage, frozen archiving down to -20°C, and incubation up to +60°C without hardening or losing retention.
Technical Specifications
| Specification | Value |
|---|---|
| Part Number (MPN) | 300-2909-020 |
| Tube OD | 9 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, and other broth media tubes during incubation to prevent contamination
- Specimen archiving — retains closure on serum, plasma, and urine tubes during refrigerated and frozen storage through multiple freeze-thaw cycles
- Clinical chemistry pre-analytical hold — friction-fit seal prevents evaporation from sample tubes awaiting analysis
- Research reagent and buffer storage — closes stock solution and working reagent tubes in 9 mm OD format
- Pneumatic tube transport — stopper retention prevents spillage and cross-contamination during in-facility specimen transport
Chemical Resistance
| Reagent / Condition | Compatibility |
|---|---|
| Aqueous buffers / saline | Excellent |
| Urine, serum, plasma matrices | Excellent |
| Broth and culture media | Excellent |
| Dilute acids and bases | Good |
| Alcohols (ethanol, isopropanol) | Good — short-term contact |
| 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 engineered to maintain friction-fit flexibility across the full -20°C to +60°C working range. LDPE's low flex modulus makes it the material of choice for stopper-style closures — rigid materials such as PP, PS, or HDPE lack the compliance needed to compress on insertion and recover to seat reliably against the inner tube wall. LabSupplies.com is an authorized Caplugs® Evergreen dealer, shipping from USA inventory with tiered volume pricing available for institutional, clinical, and grant-funded procurement programs.
Frequently Asked Questions
Why must these stoppers be LDPE rather than polypropylene or polystyrene?
Stopper-style caps rely on plug compression and elastic recovery to maintain a friction fit inside the tube. Polypropylene and polystyrene are significantly more rigid than LDPE and will crack or fail to seat rather than compress and recover — making LDPE the correct material choice for this closure format.
Will these stoppers stay in place during frozen storage and freeze-thaw cycling?
Yes. LDPE retains its flexibility down to -20°C, so the stopper maintains friction-fit engagement with the tube inner wall through repeated freeze-thaw cycles without hardening or losing retention.
Are these tube stoppers sterile?
No — they are supplied non-sterile in 1000/Bag packaging. For applications requiring sterile closures, contact your LabSupplies.com representative to confirm availability of sterile-packaged options within the Caplugs® Evergreen stopper range.
What other sizes are available in the Caplugs® Evergreen stopper range?
The Evergreen stopper line includes natural LDPE stoppers for 8 mm OD tubes (300-2908-020) and 10 mm OD tubes (300-2910-020), as well as a green 9 mm option (300-2909-G20) for color-coded tube identification workflows.