{"product_id":"caplugs-300-2908-g20-ldpe-test-tube-stopper-8mm-green","title":"Test Tube Stoppers, Thin-Wall, HDPE, Green — 300-2908-G20 | 1000\/Bag | Caplugs® Evergreen","description":"\u003ch2\u003eTest Tube Stopper Caps for 8 mm Test Tubes, LDPE, Green — 300-2908-G20 | 1000\/Bag\u003c\/h2\u003e \u003ctable\u003e \u003cthead\u003e\u003ctr\u003e\u003cth colspan=\"2\"\u003eQuick Reference — 300-2908-G20\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\u003e8 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\u003eGreen\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003e\u003cstrong\u003eTube Types\u003c\/strong\u003e\u003c\/td\u003e \u003ctd\u003eSmall-format test tubes\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003e\u003cstrong\u003eFlexibility\u003c\/strong\u003e\u003c\/td\u003e \u003ctd\u003e✓ LDPE — snap-in without cracking at -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$45.45 \/ Bag ($0.0455 \/ 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 green Low-Density Polyethylene (LDPE) stopper cap for 8 mm OD test tubes — a plug-in friction-fit closure designed for small-format test tubes, micro test tubes, and culture tubes in the 8 mm OD range. The stopper plug inserts into the tube opening and seats against the inner tube wall by friction, providing a positive retained closure that prevents evaporation, contamination, and spillage during culture incubation, specimen archiving, refrigerated storage, and pneumatic tube transport without threading or snap-over engagement. Green stoppers enable color-coded test tube routing — green is widely used in clinical and research laboratory workflows to designate specific specimen types, processing batches, or patient cohort groups, enabling rapid visual differentiation of stopper-capped tubes from other tube formats in the processing rack.\u003c\/p\u003e \u003cp\u003eLDPE is the required material for stopper-style tube caps because its low-density polyethylene flex modulus allows the stopper plug to compress under insertion force and recover to retain against the tube inner wall without fracturing — the failure mode that makes rigid materials (PS, PP, HDPE) unsuitable for stopper-format closures. LDPE maintains this flexibility across the full storage temperature range from -20°C frozen archive to +60°C incubation, ensuring stopper retention through freeze-thaw cycles without hardening or losing friction-fit engagement at low temperatures. LDPE chemical inertness to aqueous specimen matrices (urine, serum, plasma, broth media) ensures no cap leaching into tube contents during storage.\u003c\/p\u003e \u003cp\u003eAt $45.45 per 1000\/Bag — $0.0455 per stopper — the delivers 8 mm green LDPE tube closure at per-stopper economics for high-volume tube capping programs. Available across the full Caplugs® Evergreen stopper range: 300-2908-020 (Natural 8 mm, $45.45\/1000); 300-2909-G20 (Green 9 mm, $49.88\/1000); 300-2910-020 (Natural 10 mm, $44.43\/1000).\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\u003e3002908G20E1\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eTube OD\u003c\/td\u003e \u003ctd\u003e8 mm\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eCap Style\u003c\/td\u003e \u003ctd\u003eStopper — plug-in friction fit into tube opening\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\u003eGreen\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eTube Compat.\u003c\/td\u003e \u003ctd\u003eDisposable glass\/PS culture tubes\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eTemp. Range\u003c\/td\u003e \u003ctd\u003e-20°C to +60°C (LDPE flex range)\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 8 mm green LDPE stopper cap fits small-format test tubes, micro test tubes, and culture tubes in the 8 mm OD range for the following 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 broth\u003c\/td\u003e \u003ctd\u003eLDPE stopper prevents contamination during culture incubation\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eSpecimen tube archiving\u003c\/td\u003e \u003ctd\u003eSerum, plasma, urine tubes in cold storage\u003c\/td\u003e \u003ctd\u003eStopper seals tube during refrigerated and frozen archiving\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eChemistry tube sealing\u003c\/td\u003e \u003ctd\u003eClinical chemistry sample tubes\u003c\/td\u003e \u003ctd\u003eLDPE flex seal prevents evaporation during pre-analytical hold\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eResearch tube closure\u003c\/td\u003e \u003ctd\u003eReagent, buffer, stock solution tubes\u003c\/td\u003e \u003ctd\u003eStopper caps reusable glass and PS tubes between uses\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003ePneumatic tube transport\u003c\/td\u003e \u003ctd\u003eSample tube transport in pneumatic systems\u003c\/td\u003e \u003ctd\u003eLDPE flex retention maintains seal through transport forces\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eColor-coded batch routing\u003c\/td\u003e \u003ctd\u003eColor stopper = specimen type or batch designation\u003c\/td\u003e \u003ctd\u003eGreen vs Natural for visual specimen-type differentiation in racks\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eCell culture tube capping\u003c\/td\u003e \u003ctd\u003eSuspension cell culture, transfection, virus\u003c\/td\u003e \u003ctd\u003eLDPE stopper for capped incubation with gas exchange capability\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eEnvironmental sample tubes\u003c\/td\u003e \u003ctd\u003eWater, soil extract, field sample tubes\u003c\/td\u003e \u003ctd\u003eLDPE inert to aqueous environmental sample 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 and lot before bulk purchase — tube opening diameter can vary slightly between manufacturers within the 8 mm OD range. Request a free sample to confirm friction-fit retention before committing to volume.\u003c\/em\u003e\u003c\/p\u003e \u003ch2\u003eChemical Resistance — Low-Density Polyethylene (LDPE)\u003c\/h2\u003e \u003cp\u003eLDPE provides the flexibility essential for stopper-style tube caps — it compresses and springs back under insertion and removal forces without fracturing, while resisting the aqueous specimen matrices it contacts in clinical and laboratory tube workflows.\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 at -20°C\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 laboratories capping culture tubes during incubation; clinical chemistry and hematology labs archiving specimen tubes in refrigerated and frozen storage; research labs capping reagent and buffer stock tubes between uses; cell culture programs capping suspension culture tubes during incubation; environmental and field sampling programs capping sample collection tubes; and any laboratory workflow requiring friction-fit sealed closure on 8 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 on stocked inventory. \u003ca href=\"#request-sample\"\u003eRequest a free sample below\u003c\/a\u003e to validate stopper fit with your specific tube brand before committing to volume.\u003c\/p\u003e \u003ch2\u003eFrequently Asked Questions — Caplugs® Evergreen \u003c\/h2\u003e \u003ch3\u003eWhat test tube OD does the stopper fit?\u003c\/h3\u003e \u003cp\u003eThe is designed for test tubes with a 8 mm outer diameter (OD) — the tube's outer dimension. This includes Disposable glass\/PS culture tubes, small-diameter polystyrene test tubes, hematocrit tubes with stopper caps, and thin-wall tubes in micro-analytical formats. Always validate stopper-to-tube fit with a sample before bulk purchase — tube opening diameter can vary slightly between manufacturers and within the 8 mm OD range depending on wall thickness. Request a free sample to confirm friction-fit retention before committing to volume.\u003c\/p\u003e \u003ch3\u003eWhy is LDPE specified for test tube stopper caps rather than PP or PS?\u003c\/h3\u003e \u003cp\u003eStopper-style tube caps work by friction fit — the plug compresses under insertion and recovers against the inner tube wall. This requires a material with sufficient flex modulus to compress and spring back without fracturing. PP and PS are too rigid — they would crack under the repeated insertion\/removal forces of high-volume tube workflows. LDPE's low-density flex allows repeated stopper insertion and removal across thousands of cycles without fracture, while retaining enough spring-back to maintain friction-fit seal retention against the tube wall. LDPE also retains flexibility at -20°C, preventing brittle fracture during frozen archive stopper removal.\u003c\/p\u003e \u003ch3\u003eWhat is the difference between Green and Natural LDPE stoppers for 8 mm tubes?\u003c\/h3\u003e \u003cp\u003eGreen LDPE stoppers  and Natural LDPE stoppers (300-2908-020) are identical in material and performance. Green enables color-coded specimen-type routing — green stoppered tubes are visually differentiated in processing racks from natural-stoppered tubes, supporting specimen-type, batch, or priority designation without secondary labels. Choose Natural for universal use with label-based identification; choose Green when visual color routing is part of the workflow.\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 8 mm Test Tubes, Non-Sterile, Low-Density Polyethylene (LDPE), Green \\u2014 300-2908-G20 | 1000\/Bag | Caplugs\\u00ae Evergreen\",\n  \"description\": \"Caplugs\\u00ae Evergreen 300-2908-G20. LDPE test tube stopper caps for 8 mm test tubes, green, 1000\/Bag. Culture tubes, specimen archiving. BPA-free. USA.\",\n  \"sku\": \"3002908G20E1\",\n  \"mpn\": \"300-2908-G20\",\n  \"material\": \"Low-Density Polyethylene (LDPE)\",\n  \"color\": \"Green\",\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\": \"45.45\",\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\": \"8 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 OD does the 300-2908-G20 stopper fit?\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"The 300-2908-G20 is designed for test tubes with a 8 mm outer diameter (OD) \\u2014 the tube's outer dimension. This includes Disposable glass\/PS culture tubes, small-diameter polystyrene test tubes, hematocrit tubes with stopper caps, and thin-wall tubes in micro-analytical formats. Always validate stopper-to-tube fit with a sample before bulk purchase \\u2014 tube opening diameter can vary slightly between manufacturers and within the 8 mm OD range depending on wall thickness. Request a free sample to confirm friction-fit retention before committing to volume.\"\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 tube caps work by friction fit \\u2014 the plug compresses under insertion and recovers against the inner tube wall. This requires a material with sufficient flex modulus to compress and spring back without fracturing. PP and PS are too rigid \\u2014 they would crack under the repeated insertion\/removal forces of high-volume tube workflows. LDPE's low-density flex allows repeated stopper insertion and removal across thousands of cycles without fracture, while retaining enough spring-back to maintain friction-fit seal retention against the tube wall. LDPE also retains flexibility at -20\\u00b0C, preventing brittle fracture during frozen archive stopper removal.\"\n      }\n    },\n    {\n      \"@type\": \"Question\",\n      \"name\": \"What is the difference between Green and Natural LDPE stoppers for 8 mm tubes?\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"Green LDPE stoppers (300-2908-G20) and Natural LDPE stoppers (300-2908-020) are identical in material and performance. Green enables color-coded specimen-type routing \\u2014 green stoppered tubes are visually differentiated in processing racks from natural-stoppered tubes, supporting specimen-type, batch, or priority designation without secondary labels. Choose Natural for universal use with label-based identification; choose Green when visual color routing is part of the workflow.\"\n      }\n    }\n  ]\n}\n\u003c\/script\u003e","brand":"Caplugs® Evergreen","offers":[{"title":"Default Title","offer_id":48567084515560,"sku":"300-2908-G20","price":45.45,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0694\/5361\/1240\/files\/300-2908-G20_01.jpg?v=1779031395","url":"https:\/\/labsupplies.com\/products\/caplugs-300-2908-g20-ldpe-test-tube-stopper-8mm-green","provider":"LabSupplies.com","version":"1.0","type":"link"}