{"product_id":"caplugs-300-2916-r20-ldpe-test-tube-stopper-16mm-red","title":"Test Tube Stoppers, LDPE, Red — 300-2916-R20 | 1000\/Bag | Caplugs® Evergreen","description":"\u003ch2\u003e16 mm Test Tube Stoppers — LDPE, Red, 1000\/Bag (300-2916-R20)\u003c\/h2\u003e\n\u003cp\u003eThese red low-density polyethylene (LDPE) stopper caps are engineered for 16 mm OD test tubes — including standard 16 × 100 mm formats — used in clinical chemistry, serology, microbiology culture, and specimen archiving workflows. The plug-in friction-fit design relies on LDPE's characteristic flex modulus to provide consistent compression and spring-back across repeated insertion and removal cycles, maintaining a reliable seal without adhesives or secondary closures. Supplied non-sterile in 1000\/Bag, they offer a cost-effective solution for high-throughput tube management at the bench or in clinical sample-processing areas.\u003c\/p\u003e\n\n\u003ch2\u003eTechnical Specifications\u003c\/h2\u003e\n\u003ctable\u003e\n\u003cthead\u003e\u003ctr\u003e\n\u003cth\u003eSpecification\u003c\/th\u003e\n\u003cth\u003eValue\u003c\/th\u003e\n\u003c\/tr\u003e\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003ePart Number (MPN)\u003c\/td\u003e\n\u003ctd\u003e300-2916-R20\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTube OD\u003c\/td\u003e\n\u003ctd\u003e16 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCompatible Tube Format\u003c\/td\u003e\n\u003ctd\u003e16 × 100 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCap Style\u003c\/td\u003e\n\u003ctd\u003eStopper — plug-in friction fit\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMaterial\u003c\/td\u003e\n\u003ctd\u003eLow-Density Polyethylene (LDPE)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eColor\u003c\/td\u003e\n\u003ctd\u003eRed\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTemperature Range\u003c\/td\u003e\n\u003ctd\u003e-20°C to +60°C\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSterility\u003c\/td\u003e\n\u003ctd\u003eNon-Sterile\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePack Size\u003c\/td\u003e\n\u003ctd\u003e1000\/Bag\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBPA \/ Phthalates\u003c\/td\u003e\n\u003ctd\u003eBPA-free; no phthalate plasticizers\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCountry of Origin\u003c\/td\u003e\n\u003ctd\u003eUSA\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\n\u003ch2\u003eApplications\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eClinical specimen archiving:\u003c\/strong\u003e Seals serum, plasma, and whole-blood tubes during refrigerated or frozen long-term storage, preventing evaporation and cross-contamination.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMicrobiology culture tube capping:\u003c\/strong\u003e Retains flexibility at 37°C incubation temperatures, providing a stable closure for TSB, BHI, LB broth, and similar liquid media tubes.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCell culture and virus propagation:\u003c\/strong\u003e Stopper-style fit allows controlled gas exchange while blocking environmental contamination during suspension culture workflows.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eClinical tube color routing:\u003c\/strong\u003e Red mirrors the CLSI H3 red-top serum convention, supporting color-coded specimen-type identification and routing without relabeling.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePneumatic tube transport:\u003c\/strong\u003e LDPE flexibility absorbs acceleration forces encountered in clinical pneumatic transport systems without compromising the friction-fit seal.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eResearch reagent and buffer tubes:\u003c\/strong\u003e Stopper seals reusable glass and polystyrene tubes between uses during reagent preparation and stock solution archiving.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHematology and coagulation:\u003c\/strong\u003e Color-coded stoppers support anticoagulant tube designation for EDTA and citrate tube formats.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eChemical Resistance\u003c\/h2\u003e\n\u003ctable\u003e\n\u003cthead\u003e\u003ctr\u003e\n\u003cth\u003eReagent \/ Condition\u003c\/th\u003e\n\u003cth\u003eCompatibility\u003c\/th\u003e\n\u003c\/tr\u003e\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eAqueous buffers and saline\u003c\/td\u003e\n\u003ctd\u003eExcellent\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSerum and plasma\u003c\/td\u003e\n\u003ctd\u003eExcellent — inert, no leaching\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBroth media (TSB, BHI, LB)\u003c\/td\u003e\n\u003ctd\u003eExcellent\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eDilute acids and bases\u003c\/td\u003e\n\u003ctd\u003eGood\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eEthanol and isopropanol\u003c\/td\u003e\n\u003ctd\u003eGood — short-term contact; avoid prolonged immersion\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eChlorinated solvents (chloroform, DCM)\u003c\/td\u003e\n\u003ctd\u003eNot recommended\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAromatic solvents (toluene, xylene)\u003c\/td\u003e\n\u003ctd\u003eNot recommended\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFrozen storage (-20°C)\u003c\/td\u003e\n\u003ctd\u003eExcellent — LDPE retains flexibility; no brittle failure\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eIncubation (up to +60°C)\u003c\/td\u003e\n\u003ctd\u003eExcellent — seal engagement maintained\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\n\u003ch2\u003eQuality \u0026amp; Procurement\u003c\/h2\u003e\n\u003cp\u003eMade in USA, these Caplugs® Evergreen stoppers are produced from BPA-free, phthalate-free LDPE resin under ISO 9001 quality management, ensuring lot-to-lot dimensional consistency critical for reliable friction-fit retention across 16 mm tube formats. LabSupplies.com is an authorized Caplugs® Evergreen dealer shipping from USA inventory, with tiered volume pricing available for clinical labs, hospitals, and research institutions managing high-throughput tube workflows. Always validate fit against your specific tube brand before committing to bulk purchase, as 16 mm OD tubes can vary in opening diameter depending on wall thickness — contact us to request a sample.\u003c\/p\u003e\n\n\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003eAre these stoppers compatible with all 16 mm test tubes?\u003c\/strong\u003e\u003cbr\u003eThey are designed for standard 16 mm OD tubes, including the common 16 × 100 mm format. Because wall thickness varies by manufacturer, the actual opening diameter can differ slightly between tube brands. We recommend validating fit with your specific tubes — contact LabSupplies.com to request a sample before placing a bulk order.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eCan these stoppers be used for frozen specimen storage?\u003c\/strong\u003e\u003cbr\u003eYes. LDPE retains its characteristic flexibility down to -20°C, so the stopper will not become brittle or crack during removal from frozen archives — a common failure mode with more rigid cap materials.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eWhy is the red color significant in a clinical setting?\u003c\/strong\u003e\u003cbr\u003eRed mirrors the CLSI H3 red-top serum tube convention, making these stoppers a natural fit for color-coded specimen routing that designates serum-containing or no-additive tubes. Staff can identify tube type by color at a glance without retraining.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eAre these stoppers sterile, and can they be autoclaved?\u003c\/strong\u003e\u003cbr\u003eThese stoppers are supplied non-sterile. LDPE is not autoclavable — sustained exposure to steam autoclave temperatures (121°C) exceeds the material's safe temperature range of -20°C to +60°C and will deform the stopper. For sterile applications, treat with appropriate cold sterilization methods and validate before use.\u003c\/p\u003e\n\n\u003cscript type=\"application\/ld+json\"\u003e{\"@context\":\"https:\/\/schema.org\/\",\"@type\":\"Product\",\"name\":\"16 mm Test Tube Stoppers, LDPE, Red — 1000\/Bag\",\"sku\":\"300-2916-R20\",\"mpn\":\"300-2916-R20\",\"brand\":{\"@type\":\"Brand\",\"name\":\"Caplugs® Evergreen\"},\"material\":\"Low-Density Polyethylene (LDPE)\",\"color\":\"Red\",\"offers\":{\"@type\":\"Offer\",\"priceCurrency\":\"USD\",\"price\":\"66.96\",\"availability\":\"https:\/\/schema.org\/InStock\"}}\u003c\/script\u003e\n\u003cscript type=\"application\/ld+json\"\u003e{\"@context\":\"https:\/\/schema.org\/\",\"@type\":\"FAQPage\",\"mainEntity\":[{\"@type\":\"Question\",\"name\":\"Are these stoppers compatible with all 16 mm test tubes?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"They are designed for standard 16 mm OD tubes, including the common 16 × 100 mm format. 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