{"product_id":"caplugs-300-2912-b20-ldpe-test-tube-stopper-12mm-blue","title":"Test Tube Stoppers, LDPE, Blue, BD® Compatible — 300-2912-B20 | 1000\/Bag | Caplugs® Evergreen","description":"\u003ch2\u003eTest Tube Stopper Caps for 12 mm Test Tubes, LDPE, Blue — 300-2912-B20 | 1000\/Bag\u003c\/h2\u003e \u003ctable\u003e \u003cthead\u003e\u003ctr\u003e\u003cth colspan=\"2\"\u003eQuick Reference — 300-2912-B20\u003c\/th\u003e\u003c\/tr\u003e\u003c\/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd\u003e\u003cstrong\u003eTube OD\u003c\/strong\u003e\u003c\/td\u003e \u003ctd\u003e12 mm\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003e\u003cstrong\u003eCap Type\u003c\/strong\u003e\u003c\/td\u003e \u003ctd\u003eStopper (plug-in friction fit)\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003e\u003cstrong\u003eMaterial\u003c\/strong\u003e\u003c\/td\u003e \u003ctd\u003eLow-Density Polyethylene (LDPE)\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003e\u003cstrong\u003eColor\u003c\/strong\u003e\u003c\/td\u003e \u003ctd\u003eBlue\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003e\u003cstrong\u003eTube Types\u003c\/strong\u003e\u003c\/td\u003e \u003ctd\u003eStandard 12 × 75 mm\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003e\u003cstrong\u003eFlexibility\u003c\/strong\u003e\u003c\/td\u003e \u003ctd\u003e✓ LDPE — flexible fit retained -20°C to +60°C\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003e\u003cstrong\u003eSterility\u003c\/strong\u003e\u003c\/td\u003e \u003ctd\u003eNon-Sterile\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003e\u003cstrong\u003ePack Size\u003c\/strong\u003e\u003c\/td\u003e \u003ctd\u003e1000 \/ Bag\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003e\u003cstrong\u003ePrice\u003c\/strong\u003e\u003c\/td\u003e \u003ctd\u003e$44.13 \/ Bag ($0.0442 \/ stopper)\u003c\/td\u003e \u003c\/tr\u003e \u003c\/tbody\u003e \u003c\/table\u003e \u003ch2\u003eTechnical Narrative\u003c\/h2\u003e \u003cp\u003eThe Caplugs® Evergreen is a blue LDPE stopper cap for 12 mm OD test tubes — a plug-in friction-fit closure designed for 12 mm OD test tubes — a very widely used diameter across clinical, research, and culture tube formats. The 12 mm size covers clinical chemistry, hematology, microbiology, and research tube capping across the widest range of laboratory tube formats. Blue stoppers mirror the CLSI H3 convention where blue-top tubes indicate citrate anticoagulant — making blue stoppers a natural choice for post-collection blue-top tube closure and for designating citrate specimen batches in color-coded routing systems.\u003c\/p\u003e \u003cp\u003eLDPE'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.\u003c\/p\u003e \u003cp\u003eAt $44.13 per 1000\/Bag — $0.0442 per stopper — the delivers 12 mm blue tube closure at per-stopper economics for high-volume programs. Also available in this size: 300-2912-E20 (Orange 12 mm ($44.13)); 300-2912-G20 (Green 12 mm ($44.13)); 300-2911-020 (Natural 11 mm ($48.09)).\u003c\/p\u003e \u003ch2\u003eTechnical Specifications — Caplugs® Evergreen \u003c\/h2\u003e \u003ctable\u003e \u003cthead\u003e\u003ctr\u003e \u003cth\u003eSpecification\u003c\/th\u003e \u003cth\u003eValue\u003c\/th\u003e \u003c\/tr\u003e\u003c\/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd\u003ePart Number\u003c\/td\u003e \u003ctd\u003e\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eCaplugs Item #\u003c\/td\u003e \u003ctd\u003e3002912B20E1\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eTube OD\u003c\/td\u003e \u003ctd\u003e12 mm\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eCap Style\u003c\/td\u003e \u003ctd\u003eStopper — plug-in friction fit\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eMaterial\u003c\/td\u003e \u003ctd\u003eLow-Density Polyethylene (LDPE)\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eColor\u003c\/td\u003e \u003ctd\u003eBlue\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eTube Compat.\u003c\/td\u003e \u003ctd\u003eStandard 12 × 75 mm\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eTemp. Range\u003c\/td\u003e \u003ctd\u003e-20°C to +60°C\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eSterility\u003c\/td\u003e \u003ctd\u003eNon-Sterile\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003ePack Size\u003c\/td\u003e \u003ctd\u003e1000 \/ Bag\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eBPA\/Phthalate\u003c\/td\u003e \u003ctd\u003eBPA-free; no phthalate plasticizers\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eCountry of Origin\u003c\/td\u003e \u003ctd\u003eMade in U.S.A. (California)\u003c\/td\u003e \u003c\/tr\u003e \u003c\/tbody\u003e \u003c\/table\u003e \u003ch2\u003eTest Tube Stopper Application Compatibility — \u003c\/h2\u003e \u003cp\u003eThe 12 mm blue LDPE stopper cap is designed for 12 mm OD test tubes — a very widely used diameter across clinical, research, and culture tube formats. Compatible workflows:\u003c\/p\u003e \u003ctable\u003e \u003cthead\u003e\u003ctr\u003e \u003cth\u003eApplication\u003c\/th\u003e \u003cth\u003eTube \/ Specimen Type\u003c\/th\u003e \u003cth\u003eNotes\u003c\/th\u003e \u003c\/tr\u003e\u003c\/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd\u003eCulture tube capping\u003c\/td\u003e \u003ctd\u003eMicrobiology culture tubes, TSB, BHI, LB broth\u003c\/td\u003e \u003ctd\u003eLDPE stopper seals tube during incubation; flexible fit retained at 37°C\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eSpecimen tube archiving\u003c\/td\u003e \u003ctd\u003eSerum, plasma, urine in refrigerated\/frozen storage\u003c\/td\u003e \u003ctd\u003eStopper prevents evaporation during extended cold storage\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eChemistry tube sealing\u003c\/td\u003e \u003ctd\u003eClinical chemistry sample tubes pre-analysis\u003c\/td\u003e \u003ctd\u003eLDPE inert to serum\/plasma matrix; no leaching into specimen\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eCell culture tube capping\u003c\/td\u003e \u003ctd\u003eSuspension cell culture, virus propagation\u003c\/td\u003e \u003ctd\u003eStopper allows gas exchange while preventing contamination\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003ePneumatic tube transport\u003c\/td\u003e \u003ctd\u003eSample tube transport in clinical tube systems\u003c\/td\u003e \u003ctd\u003eLDPE flex retention survives transport acceleration forces\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eColor-coded batch routing\u003c\/td\u003e \u003ctd\u003eVisual specimen-type or priority designation\u003c\/td\u003e \u003ctd\u003eColor-stop tubes differentiated visually in loading racks\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eResearch reagent tube caps\u003c\/td\u003e \u003ctd\u003eBuffer, reagent, stock solution tube closure\u003c\/td\u003e \u003ctd\u003eStopper seals reusable glass and PS tubes between uses\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eEnvironmental sample tubes\u003c\/td\u003e \u003ctd\u003eWater, soil, field collection tubes\u003c\/td\u003e \u003ctd\u003eLDPE chemical inertness to aqueous environmental matrices\u003c\/td\u003e \u003c\/tr\u003e \u003c\/tbody\u003e \u003c\/table\u003e \u003cp\u003e\u003cem\u003eAlways validate stopper fit with your specific tube brand before bulk purchase — 12 mm OD tubes vary in opening diameter by wall thickness. Request a free sample to confirm friction-fit retention before volume commitment.\u003c\/em\u003e\u003c\/p\u003e \u003ch2\u003eChemical Resistance — Low-Density Polyethylene (LDPE)\u003c\/h2\u003e \u003cp\u003eLDPE provides the flexibility essential for stopper-format tube caps and broad chemical inertness to standard laboratory specimen matrices.\u003c\/p\u003e \u003ctable\u003e \u003cthead\u003e\u003ctr\u003e \u003cth\u003eReagent \/ Condition\u003c\/th\u003e \u003cth\u003eCompatibility\u003c\/th\u003e \u003c\/tr\u003e\u003c\/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd\u003eAqueous buffers \/ water\u003c\/td\u003e \u003ctd\u003e✓ Excellent\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eUrine \/ serum \/ plasma\u003c\/td\u003e \u003ctd\u003e✓ Excellent\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eCell culture media\u003c\/td\u003e \u003ctd\u003e✓ Excellent\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eDilute acids (\u0026lt;10%)\u003c\/td\u003e \u003ctd\u003e✓ Good\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eDilute alkalies (pH \u0026lt;12)\u003c\/td\u003e \u003ctd\u003e✓ Good\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eShort-chain alcohols (brief)\u003c\/td\u003e \u003ctd\u003e✓ Good\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eDMSO (≤10%)\u003c\/td\u003e \u003ctd\u003e✓ Good — brief contact\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eConcentrated organic solvents\u003c\/td\u003e \u003ctd\u003e✗ Not recommended\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eAutoclave (121°C)\u003c\/td\u003e \u003ctd\u003e✗ Not compatible — LDPE softens\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eStorage at -20°C\u003c\/td\u003e \u003ctd\u003e✓ Suitable — LDPE retains flexibility\u003c\/td\u003e \u003c\/tr\u003e \u003c\/tbody\u003e \u003c\/table\u003e \u003ch2\u003eLaboratory Applications\u003c\/h2\u003e \u003cp\u003eThe 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 12 mm OD test tubes.\u003c\/p\u003e \u003ch2\u003eU.S. Manufacturing, Quality \u0026amp; Institutional Procurement\u003c\/h2\u003e \u003cp\u003eEvery 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. \u003ca href=\"#request-sample\"\u003eRequest a free sample below\u003c\/a\u003e to validate stopper fit with your tube brand before committing to volume.\u003c\/p\u003e \u003ch2\u003eFrequently Asked Questions — Caplugs® Evergreen \u003c\/h2\u003e \u003ch3\u003eWhat test tube formats use 12 mm OD and fit the stopper?\u003c\/h3\u003e \u003cp\u003eThe fits 12 mm outer diameter test tubes. Compatible formats include: Standard 12 × 75 mm, 12 × 100 mm glass and PS culture tubes, BD Vacutainer-compatible collection tubes, and common clinical polypropylene test tubes. Always validate stopper-to-tube fit with a sample set before bulk purchase — tube opening diameter varies within the 12 mm OD range depending on glass or plastic wall thickness. Request a free sample to confirm friction-fit retention before committing to volume.\u003c\/p\u003e \u003ch3\u003eWhat are the color conventions for 12 mm tube stoppers — Blue, Orange, and Green?\u003c\/h3\u003e \u003cp\u003eAll three 12 mm LDPE stopper colors are identical in material and friction-fit performance — the difference is color routing only. Blue : mirrors the CLSI H3 blue-top citrate anticoagulant convention — used to designate citrate specimen batches or post-collection closure of blue-top clinical tubes. Orange (300-2912-E20): high-visibility designation for STAT or priority specimens — orange stoppers stand out immediately in loading racks for urgent specimen routing. Green (300-2912-G20): general color-coded specimen-type or batch designation. Choose color based on your laboratory's tube routing color-coding protocol.\u003c\/p\u003e \u003ch3\u003eWhy is LDPE specified for test tube stopper caps rather than PP or PS?\u003c\/h3\u003e \u003cp\u003eStopper-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).\u003c\/p\u003e \u003cscript type=\"application\/ld+json\"\u003e\n{\n  \"@context\": \"https:\/\/schema.org\",\n  \"@type\": \"Product\",\n  \"name\": \"Test Tube Stopper Caps, For 12 mm Test Tubes, Non-Sterile, Low-Density Polyethylene (LDPE), Blue \\u2014 300-2912-B20 | 1000\/Bag | Caplugs\\u00ae Evergreen\",\n  \"description\": \"Caplugs\\u00ae Evergreen 300-2912-B20. LDPE test tube stopper caps, 12 mm, blue, 1000\/Bag. Culture tubes, specimen archiving. BPA-free. USA.\",\n  \"sku\": \"3002912B20E1\",\n  \"mpn\": \"300-2912-B20\",\n  \"material\": \"Low-Density Polyethylene (LDPE)\",\n  \"color\": \"Blue\",\n  \"brand\": {\n    \"@type\": \"Brand\",\n    \"name\": \"Caplugs\\u00ae Evergreen\"\n  },\n  \"manufacturer\": {\n    \"@type\": \"Organization\",\n    \"name\": \"Caplugs\\u00ae Evergreen\",\n    \"address\": {\n      \"@type\": \"PostalAddress\",\n      \"addressCountry\": \"US\",\n      \"addressRegion\": \"CA\"\n    }\n  },\n  \"offers\": {\n    \"@type\": \"Offer\",\n    \"price\": \"44.13\",\n    \"priceCurrency\": \"USD\",\n    \"availability\": \"https:\/\/schema.org\/InStock\",\n    \"itemCondition\": \"https:\/\/schema.org\/NewCondition\",\n    \"seller\": {\n      \"@type\": \"Organization\",\n      \"name\": \"LabSupplies\"\n    }\n  },\n  \"additionalProperty\": [\n    {\n      \"@type\": \"PropertyValue\",\n      \"name\": \"Tube OD\",\n      \"value\": \"12 mm\"\n    },\n    {\n      \"@type\": \"PropertyValue\",\n      \"name\": \"Cap Style\",\n      \"value\": \"Stopper (plug-in friction fit)\"\n    },\n    {\n      \"@type\": \"PropertyValue\",\n      \"name\": \"Pack Size\",\n      \"value\": \"1000 \/ Bag\"\n    },\n    {\n      \"@type\": \"PropertyValue\",\n      \"name\": \"Sterility\",\n      \"value\": \"Non-Sterile\"\n    },\n    {\n      \"@type\": \"PropertyValue\",\n      \"name\": \"Country of Origin\",\n      \"value\": \"United States\"\n    },\n    {\n      \"@type\": \"PropertyValue\",\n      \"name\": \"BPA Free\",\n      \"value\": \"Yes\"\n    }\n  ]\n}\n\u003c\/script\u003e \u003cscript type=\"application\/ld+json\"\u003e\n{\n  \"@context\": \"https:\/\/schema.org\",\n  \"@type\": \"FAQPage\",\n  \"mainEntity\": [\n    {\n      \"@type\": \"Question\",\n      \"name\": \"What test tube formats use 12 mm OD and fit the 300-2912-B20 stopper?\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"The 300-2912-B20 fits 12 mm outer diameter test tubes. Compatible formats include: Standard 12 \\u00d7 75 mm, 12 \\u00d7 100 mm glass and PS culture tubes, BD Vacutainer-compatible collection tubes, and common clinical polypropylene test tubes. Always validate stopper-to-tube fit with a sample set before bulk purchase \\u2014 tube opening diameter varies within the 12 mm OD range depending on glass or plastic wall thickness. Request a free sample to confirm friction-fit retention before committing to volume.\"\n      }\n    },\n    {\n      \"@type\": \"Question\",\n      \"name\": \"What are the color conventions for 12 mm tube stoppers \\u2014 Blue, Orange, and Green?\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"All three 12 mm LDPE stopper colors are identical in material and friction-fit performance \\u2014 the difference is color routing only. Blue (300-2912-B20): mirrors the CLSI H3 blue-top citrate anticoagulant convention \\u2014 used to designate citrate specimen batches or post-collection closure of blue-top clinical tubes. Orange (300-2912-E20): high-visibility designation for STAT or priority specimens \\u2014 orange stoppers stand out immediately in loading racks for urgent specimen routing. Green (300-2912-G20): general color-coded specimen-type or batch designation. Choose color based on your laboratory's tube routing color-coding protocol.\"\n      }\n    },\n    {\n      \"@type\": \"Question\",\n      \"name\": \"Why is LDPE specified for test tube stopper caps rather than PP or PS?\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"Stopper-style caps require a material with sufficient flex modulus to compress under insertion and spring back for friction retention \\u2014 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\\u00b0C to prevent brittle failure during frozen archive stopper removal, and provides chemical inertness to clinical specimen matrices (urine, serum, plasma, broth).\"\n      }\n    }\n  ]\n}\n\u003c\/script\u003e","brand":"Caplugs® Evergreen","offers":[{"title":"Default Title","offer_id":48567091331304,"sku":"300-2912-B20","price":44.13,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0694\/5361\/1240\/files\/300-2912-B20_01.jpg?v=1779031664","url":"https:\/\/labsupplies.com\/products\/caplugs-300-2912-b20-ldpe-test-tube-stopper-12mm-blue","provider":"LabSupplies.com","version":"1.0","type":"link"}