{"product_id":"round-bottom-test-tubes-21ml-16-x-150mm-screw-cap-ps-2222099050e1","title":"21 mL Test Tubes, Screw Caps, PS, Natural — 222-2099-050 | 25\/Bag | Caplugs® Evergreen","description":"\u003ch2\u003e21 mL Round Bottom Test Tubes with Natural Screw Caps — PS, Sterile, 16 × 150 mm (222-2099-050)\u003c\/h2\u003e\n\u003cp\u003eThese 21 mL polystyrene round-bottom test tubes ship sterile and unassembled — tubes and natural screw caps packaged separately within each 25\/Bag unit for assembly immediately before use. At 16 × 150 mm, the round-bottom geometry concentrates cell pellets and precipitates at the tube base for efficient resuspension and aspiration after centrifugation, while the threaded natural screw cap delivers a leak-resistant closure for specimen containment during storage and transport. The optical clarity of polystyrene makes these tubes a standard choice for flow cytometry, immunofluorescence, and cell sorting workflows.\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\u003e222-2099-050\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eVolume\u003c\/td\u003e\n\u003ctd\u003e21 mL\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eDimensions\u003c\/td\u003e\n\u003ctd\u003e16 × 150 mm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBottom Style\u003c\/td\u003e\n\u003ctd\u003eRound Bottom\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCap Style\u003c\/td\u003e\n\u003ctd\u003eNatural Screw Cap\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAssembly\u003c\/td\u003e\n\u003ctd\u003eUnassembled\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMaterial\u003c\/td\u003e\n\u003ctd\u003ePolystyrene (PS)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eColor\u003c\/td\u003e\n\u003ctd\u003eNatural\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSterility\u003c\/td\u003e\n\u003ctd\u003eSterile\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePack Size\u003c\/td\u003e\n\u003ctd\u003e25\/Bag\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBPA \/ Phthalate Free\u003c\/td\u003e\n\u003ctd\u003eYes\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\u003eFlow cytometry and FACS analysis — round-bottom PS format is the standard tube geometry for most flow cytometer sample ports\u003c\/li\u003e\n\u003cli\u003eImmunofluorescence staining — polystyrene optical clarity supports visual and instrument-based inspection of fluorescent samples\u003c\/li\u003e\n\u003cli\u003eCell sorting — round bottom concentrates sorted cell populations for downstream recovery\u003c\/li\u003e\n\u003cli\u003eHematology sample preparation — 21 mL capacity accommodates larger-volume whole-blood and buffy-coat workflows\u003c\/li\u003e\n\u003cli\u003eSerological and agglutination assays — round-bottom geometry provides a defined endpoint for agglutination reading\u003c\/li\u003e\n\u003cli\u003eSpecimen collection and general sample handling — threaded screw cap ensures secure containment during centrifugation, transport, and storage\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 \/ saline \/ PBS\u003c\/td\u003e\n\u003ctd\u003eExcellent\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eDilute acids\u003c\/td\u003e\n\u003ctd\u003eGood\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eDilute bases\u003c\/td\u003e\n\u003ctd\u003eGood\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMethanol\u003c\/td\u003e\n\u003ctd\u003eGood — short-term contact\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eIsopropanol\u003c\/td\u003e\n\u003ctd\u003eGood — short-term contact\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAcetonitrile\u003c\/td\u003e\n\u003ctd\u003eGood — short-term contact\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAromatic \/ chlorinated solvents\u003c\/td\u003e\n\u003ctd\u003eNot recommended\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAutoclave \/ heat sterilization\u003c\/td\u003e\n\u003ctd\u003eNot recommended — PS is not autoclavable\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 test tubes are manufactured at ISO-certified facilities using virgin-grade, FDA-registered polystyrene resin that is BPA-free and phthalate-free. Lot-level quality controls ensure consistent tube geometry, wall thickness, and dimensional uniformity across every bag. LabSupplies.com is an authorized Caplugs® Evergreen dealer shipping from USA inventory, with tiered volume pricing available for clinical labs, research institutions, and biotech facilities operating under CAP, CLIA, or ISO 15189 accreditation.\u003c\/p\u003e\n\n\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003eAre these tubes sterile when they arrive?\u003c\/strong\u003e\u003cbr\u003eYes — part number 222-2099-050 is supplied sterile. Tubes and caps are packaged separately within the sealed bag and should be assembled immediately before use to maintain sterility at the point of use.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eWhy are the tubes and caps packaged unassembled?\u003c\/strong\u003e\u003cbr\u003eShipping tubes and caps separately prevents cap deformation and ensures the threaded closure seats correctly when assembled fresh before use, maintaining a reliable leak-resistant seal.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eAre polystyrene tubes suitable for centrifugation?\u003c\/strong\u003e\u003cbr\u003ePS tubes are compatible with standard low- to moderate-speed centrifugation as used in cell pelleting and sample preparation. Confirm the g-force limits with your centrifuge rotor specifications; PS is generally not rated for high-speed ultracentrifugation applications.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eCan these tubes be used with standard flow cytometers?\u003c\/strong\u003e\u003cbr\u003eRound-bottom 12 × 75 mm tubes are the more common flow cytometry format, but many instruments and sample-handling racks also accommodate the 16 × 150 mm format. Verify that your cytometer's sample port or tube holder accepts 16 mm diameter tubes before ordering for automated workflows.\u003c\/p\u003e\n\n\u003cscript type=\"application\/ld+json\"\u003e{\"@context\":\"https:\/\/schema.org\/\",\"@type\":\"Product\",\"name\":\"21 mL Round Bottom Test Tubes with Natural Screw Caps, PS, Sterile, 16 × 150 mm — 25\/Bag\",\"sku\":\"2222099050E1\",\"mpn\":\"222-2099-050\",\"brand\":{\"@type\":\"Brand\",\"name\":\"Caplugs® Evergreen\"},\"material\":\"Polystyrene (PS)\",\"color\":\"Natural\",\"offers\":{\"@type\":\"Offer\",\"priceCurrency\":\"USD\",\"price\":\"213.73\",\"availability\":\"https:\/\/schema.org\/InStock\"}}\u003c\/script\u003e\n\n\u003cscript type=\"application\/ld+json\"\u003e{\"@context\":\"https:\/\/schema.org\/\",\"@type\":\"FAQPage\",\"mainEntity\":[{\"@type\":\"Question\",\"name\":\"Are these tubes sterile when they arrive?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Yes — they are supplied sterile. 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