{"product_id":"caplugs-300-4708-020-ldpe-flat-top-stopper-8mm-natural","title":"Test Tube Stoppers, HDPE, Natural — 300-4708-020 | 1000\/Bag | Caplugs® Evergreen","description":"\u003ch2\u003eFlat Top Test Tube Stopper Caps, For 8 mm Test Tubes, LDPE, Natural — 300-4708-020 | 1000\/Bag\u003c\/h2\u003e \u003ctable\u003e \u003cthead\u003e\u003ctr\u003e\u003cth colspan=\"2\"\u003eQuick Reference — 300-4708-020\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\u003eFlat-top stopper (plug-in friction fit)\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003e\u003cstrong\u003eProfile\u003c\/strong\u003e\u003c\/td\u003e \u003ctd\u003eFlat top — flush with tube rim when seated\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\u003eNatural\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003e\u003cstrong\u003evs Standard\u003c\/strong\u003e\u003c\/td\u003e \u003ctd\u003eFlat top sits flush; standard stopper has dome profile\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003e\u003cstrong\u003eTemp Range\u003c\/strong\u003e\u003c\/td\u003e \u003ctd\u003e-20°C to +60°C (LDPE flex range)\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$57.85 \/ Bag ($0.0579 \/ 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 natural LDPE flat-top stopper cap for 8 mm OD test tubes — the flat-profile variant of the friction-fit stopper cap design. The flat-top profile positions the cap top surface flush with the tube rim when fully seated, rather than projecting above it as a standard dome stopper would. This flush profile provides two advantages: (1) improved stacking in test tube racks — flat-top stoppers allow tubes to be stacked or inverted without the cap profile preventing full seating in rack positions; (2) reduced cap protrusion in automated tube handling systems and tube readers where a projecting dome cap can interfere with instrument clearance.\u003c\/p\u003e \u003cp\u003eLDPE construction provides the flex required for friction-fit stopper retention across repeated insertion\/removal cycles — the same material rationale as the 300-29xx series standard dome stoppers. LDPE retains flexibility from -20°C through 60°C and is chemically inert to serum, plasma, and standard aqueous specimen matrices. At $57.85 per 1000\/Bag — $0.0579 per stopper — the flat-top format delivers per-unit economics for high-volume 8 mm tube programs.\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\u003e3004708020E1\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\u003eFlat-top stopper — plug-in friction fit\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eProfile\u003c\/td\u003e \u003ctd\u003eFlat top — cap top flush with tube rim when fully seated\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\u003eNatural\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eTube Types\u003c\/td\u003e \u003ctd\u003e8 mm OD glass and PP\/PS test tubes\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\u003eFlat Top Stopper Application Compatibility — 8 mm Tubes\u003c\/h2\u003e \u003cp\u003eThe LDPE flat-top stopper fits 8 mm OD test tubes for:\u003c\/p\u003e \u003ctable\u003e \u003cthead\u003e\u003ctr\u003e \u003cth\u003eApplication\u003c\/th\u003e \u003cth\u003eTube \/ Specimen\u003c\/th\u003e \u003cth\u003eNotes\u003c\/th\u003e \u003c\/tr\u003e\u003c\/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd\u003e8 mm test tube capping\u003c\/td\u003e \u003ctd\u003e8 mm OD glass and plastic test tubes\u003c\/td\u003e \u003ctd\u003eFlat-top LDPE stopper — friction fit into tube opening\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eCulture tube closure\u003c\/td\u003e \u003ctd\u003eMicrobiology broth culture in 8 mm tubes\u003c\/td\u003e \u003ctd\u003eFlat top profile vs standard dome stopper\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eSpecimen tube archiving\u003c\/td\u003e \u003ctd\u003eSerum, plasma in refrigerated\/frozen storage\u003c\/td\u003e \u003ctd\u003eLDPE stopper seals tube during cold storage\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eColor routing (natural)\u003c\/td\u003e \u003ctd\u003eUniversal cap for any labeling system\u003c\/td\u003e \u003ctd\u003eNatural LDPE for secondary label identification\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eReagent \/ stock tube\u003c\/td\u003e \u003ctd\u003eBuffer, enzyme, reagent aliquots in 8 mm\u003c\/td\u003e \u003ctd\u003eFlat-top stopper as reusable tube closure\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eClinical chemistry tubes\u003c\/td\u003e \u003ctd\u003ePre-analysis 8 mm sample tube closure\u003c\/td\u003e \u003ctd\u003eFlat profile flush with tube rim for rack stacking\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eHematology tubes\u003c\/td\u003e \u003ctd\u003e8 mm EDTA and anticoagulant tube formats\u003c\/td\u003e \u003ctd\u003eLDPE inert to anticoagulant specimens\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eReplacement caps\u003c\/td\u003e \u003ctd\u003eReplacement for lost\/damaged tube closures\u003c\/td\u003e \u003ctd\u003e1000\/Bag bulk format for high-volume programs\u003c\/td\u003e \u003c\/tr\u003e \u003c\/tbody\u003e \u003c\/table\u003e \u003cp\u003e\u003cem\u003eValidate stopper fit with your tube brand before bulk purchase. Request a free sample to confirm friction-fit retention.\u003c\/em\u003e\u003c\/p\u003e \u003ch2\u003eChemical Resistance — Low-Density Polyethylene (LDPE)\u003c\/h2\u003e \u003cp\u003eLDPE provides flexibility for stopper friction-fit retention and inertness to clinical 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\u003eDilute acids (\u0026lt;10%)\u003c\/td\u003e \u003ctd\u003e✓ Good\u003c\/td\u003e \u003c\/tr\u003e \u003ctr\u003e \u003ctd\u003eShort-chain alcohols\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\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 chemistry and hematology laboratories using 8 mm test tubes in automated tube readers or stacking rack formats where flat-profile stoppers reduce clearance conflicts; microbiology programs capping 8 mm culture tubes for incubation; and any 8 mm test tube workflow where the flat-top stopper profile is preferred over the standard dome.\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. We supply reference laboratories, hospital systems, and federal procurement offices under institutional pricing programs. \u003ca href=\"#request-sample\"\u003eRequest a free sample below\u003c\/a\u003e to validate fit before committing to volume.\u003c\/p\u003e \u003ch2\u003eFrequently Asked Questions — Caplugs® Evergreen \u003c\/h2\u003e \u003ch3\u003eWhat is the difference between a flat-top stopper and a standard dome stopper for 8 mm tubes?\u003c\/h3\u003e \u003cp\u003eThe flat-top stopper  has a flat top surface that sits flush with the tube rim when fully seated. Standard dome stoppers (e.g., 300-2908 series) have a convex dome that projects above the tube rim. The flat top is preferred in rack-stacking programs where dome projections interfere with full seating, and in automated tube handling where instrument clearance is tight. Both are LDPE friction-fit stoppers with identical tube compatibility for 8 mm OD tubes.\u003c\/p\u003e \u003ch3\u003eIs the flat-top stopper compatible with the same 8 mm tubes as the dome stoppers?\u003c\/h3\u003e \u003cp\u003eYes. The fits the same 8 mm OD test tube formats as the standard dome stoppers (300-2908-020 natural, 300-2908-G20 green). All 8 mm stoppers in the Caplugs® Evergreen range are LDPE friction-fit for 8 mm OD glass and PP\/PS test tubes. The only functional difference between flat-top and dome-top is the cap profile above the tube rim. Validate fit with a sample before bulk purchase.\u003c\/p\u003e \u003ch3\u003eWhy is LDPE used for stopper caps rather than PP or HDPE?\u003c\/h3\u003e \u003cp\u003eLDPE's low-density flex modulus provides the compression and spring-back required for friction-fit stopper retention across repeated insertion\/removal cycles. PP and HDPE are too rigid for stopper-style plug-in engagement — they crack under repeated insertion\/removal rather than flexing. LDPE also retains flexibility at -20°C to prevent brittle fracture during frozen stopper removal. For screw-thread tube caps (300-3010\/300-3532\/300-3541), HDPE is the correct material — but for friction-fit stoppers, LDPE is the only appropriate specification.\u003c\/p\u003e \u003cscript type=\"application\/ld+json\"\u003e\n{\n  \"@context\": \"https:\/\/schema.org\",\n  \"@type\": \"Product\",\n  \"name\": \"Flat Top Test Tube Stopper Caps, For 8 mm Test Tubes, Non-Sterile, Low-Density Polyethylene (LDPE), Natural \\u2014 300-4708-020 | 1000\/Bag | Caplugs\\u00ae Evergreen\",\n  \"description\": \"Caplugs\\u00ae Evergreen 300-4708-020. LDPE flat top stopper caps for 8 mm test tubes, natural, 1000\/Bag. Flush profile. BPA-free. USA.\",\n  \"sku\": \"3004708020E1\",\n  \"mpn\": \"300-4708-020\",\n  \"material\": \"Low-Density Polyethylene (LDPE)\",\n  \"color\": \"Natural\",\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\": \"57.85\",\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\": \"Cap Profile\",\n      \"value\": \"Flat Top Stopper\"\n    },\n    {\n      \"@type\": \"PropertyValue\",\n      \"name\": \"Tube OD\",\n      \"value\": \"8 mm\"\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 is the difference between a flat-top stopper and a standard dome stopper for 8 mm tubes?\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"The flat-top stopper (300-4708-020) has a flat top surface that sits flush with the tube rim when fully seated. Standard dome stoppers (e.g., 300-2908 series) have a convex dome that projects above the tube rim. The flat top is preferred in rack-stacking programs where dome projections interfere with full seating, and in automated tube handling where instrument clearance is tight. Both are LDPE friction-fit stoppers with identical tube compatibility for 8 mm OD tubes.\"\n      }\n    },\n    {\n      \"@type\": \"Question\",\n      \"name\": \"Is the 300-4708-020 flat-top stopper compatible with the same 8 mm tubes as the dome stoppers?\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"Yes. The 300-4708-020 fits the same 8 mm OD test tube formats as the standard dome stoppers (300-2908-020 natural, 300-2908-G20 green). All 8 mm stoppers in the Caplugs\\u00ae Evergreen range are LDPE friction-fit for 8 mm OD glass and PP\/PS test tubes. The only functional difference between flat-top and dome-top is the cap profile above the tube rim. Validate fit with a sample before bulk purchase.\"\n      }\n    },\n    {\n      \"@type\": \"Question\",\n      \"name\": \"Why is LDPE used for stopper caps rather than PP or HDPE?\",\n      \"acceptedAnswer\": {\n        \"@type\": \"Answer\",\n        \"text\": \"LDPE's low-density flex modulus provides the compression and spring-back required for friction-fit stopper retention across repeated insertion\/removal cycles. PP and HDPE are too rigid for stopper-style plug-in engagement \\u2014 they crack under repeated insertion\/removal rather than flexing. LDPE also retains flexibility at -20\\u00b0C to prevent brittle fracture during frozen stopper removal. For screw-thread tube caps (300-3010\/300-3532\/300-3541), HDPE is the correct material \\u2014 but for friction-fit stoppers, LDPE is the only appropriate specification.\"\n      }\n    }\n  ]\n}\n\u003c\/script\u003e","brand":"Caplugs® Evergreen","offers":[{"title":"Default Title","offer_id":48568517001448,"sku":"300-4708-020","price":57.85,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0694\/5361\/1240\/files\/300-4708-020_01.jpg?v=1779115833","url":"https:\/\/labsupplies.com\/products\/caplugs-300-4708-020-ldpe-flat-top-stopper-8mm-natural","provider":"LabSupplies.com","version":"1.0","type":"link"}