Two-Position Snap Caps for 12 mm PS Test Tubes — LDPE, Natural (300-3812-02S), 1000/Bag
These Caplugs® Evergreen LDPE snap caps are engineered specifically for 12 mm polystyrene (PS) test tubes and offer two distinct functional positions without ever leaving the tube. The partial-open first position allows CO₂ and O₂ gas exchange during microbiology culture incubation, while the fully closed second position seals the tube completely for storage, freezing, or transport — all without removing the cap from the tube between steps. Supplied non-sterile in 1000/Bag bulk packaging, part number 300-3812-02S is the PS tube variant of this two-position snap cap.
Technical Specifications
| Specification | Value |
|---|---|
| Part Number (MPN) | 300-3812-02S |
| Tube Format | 12 mm PS (polystyrene) test tubes |
| Cap Style | Two-position snap cap |
| Position 1 | Partial-open — gas exchange / venting |
| Position 2 | Fully closed — sealed for storage and transport |
| Material | Low-Density Polyethylene (LDPE) |
| Color | Natural |
| Sterility | Non-Sterile |
| Pack Size | 1000/Bag |
| BPA / Phthalates | BPA-free; no phthalate plasticizers |
| Country of Origin | USA (California) |
Applications
- Microbiology culture tube capping: The partial-open position supports aerobic and microaerophilic broth culture workflows (TSB, BHI, LB) by maintaining required gas exchange during incubation without exposing the open tube to environmental contaminants.
- Refrigerated and frozen sample storage: The fully closed snap position creates a sealed closure that prevents contamination, evaporation, and cross-contamination during refrigerated holds or frozen archiving.
- Clinical chemistry and pre-analytical tube staging: The closed position prevents analyte evaporation from sample tubes awaiting analysis, preserving specimen integrity through the pre-analytical phase.
- Cell culture and virus propagation tubes: Suspension culture and viral propagation workflows benefit from the partial-open gas exchange position during incubation and the sealed position for safe transport between laboratory areas.
- Environmental and field collection: The closed snap position secures collected specimens during field transport; tubes can be transitioned to the partial-open position without handling a separate stopper.
- High-cycle open/close workflows: Because the cap remains attached in both positions, tubes accessed repeatedly throughout a workflow never require re-capping with a separate stopper, reducing handling errors and cap loss.
Chemical Resistance
| Reagent / Condition | Compatibility |
|---|---|
| Aqueous buffers and saline | Excellent |
| Dilute acids and bases | Good |
| Ethanol and isopropanol (dilute) | Good — short-term contact |
| Acetone / chlorinated solvents | Not recommended |
| Autoclave sterilization | Not recommended (LDPE softens at autoclave temperatures) |
Quality & Procurement
Made in USA (California), these snap caps are manufactured by Caplugs® Evergreen from BPA-free, phthalate-free LDPE resin. The inherent flexibility of low-density polyethylene is precisely what enables the snap-position engagement mechanism to perform reliably through the repeated open/close cycling of demanding microbiology and clinical workflows. LabSupplies.com is an authorized Caplugs® Evergreen dealer and ships from USA inventory, with tiered pricing available for high-volume institutional and grant-funded purchasing programs. Laboratories requiring a cap for 12 mm PP test tubes should see the companion part 300-3812-02P, which shares the same two-position design in the same LDPE material but is dimensioned for PP tube outside diameters.
Frequently Asked Questions
What is the difference between Position 1 and Position 2 on these snap caps?
Position 1 is a partial-open state that holds the cap ajar, allowing gas exchange — critical during aerobic or microaerophilic culture incubation. Position 2 is the fully closed, sealed state used for storage, freezing, and transport. Importantly, the cap never leaves the tube when moving between positions, eliminating the risk of cap loss or mix-up.
Can these caps be used on PP test tubes instead of PS tubes?
No — the 300-3812-02S is dimensioned specifically for 12 mm PS (polystyrene) test tubes. For 12 mm PP (polypropylene) tubes, the correct replacement is the companion part 300-3812-02P. Using a cap designed for PS tubes on PP tubes may result in a loose or improperly sealing fit.
Are these snap caps sterile?
No — they are supplied non-sterile in 1000/Bag bulk packaging. For workflows requiring sterile closures, check whether your aseptic technique or downstream sterilization protocol is compatible with LDPE, keeping in mind that LDPE is not autoclavable.
How do these compare to simple stopper caps for culture tube workflows?
Unlike a traditional stopper, which must be physically removed and set aside when venting is needed, the two-position snap cap remains attached to the tube throughout both open and closed states. This prevents stopper contamination from benchtop surfaces, reduces handling steps, and eliminates the problem of misplacing or mismatching stoppers during high-throughput incubation runs.