{"product_id":"214-2099-y50-round-bottom-screw-cap-tube","title":"15–21 mL Test Tubes, Screw Caps, PS, Yellow — 214-2099-Y50 | 1000\/Bag | Caplugs® Evergreen","description":"\u003ch2\u003e21 mL Round-Bottom Test Tubes with Yellow Screw Caps — PS, 16 × 150 mm, 1000\/Bag (214-2099-Y50)\u003c\/h2\u003e\n\u003cp\u003eThese 21 mL polystyrene round-bottom test tubes ship with matching yellow screw caps, unassembled, in a 1000\/Bag pack — making them the largest round-bottom tube in the Caplugs® Evergreen catalog and well suited to bulk reagent preparation, extended inversion mixing, and large-volume culture or reaction workflows. The 16 × 150 mm format fits standard 16 mm tube racks, and the yellow screw cap provides a leak-resistant re-closure for sample storage, transport, and reflex testing without the need for aliquot transfer. Bearing part number 214-2099-Y50, these tubes are supplied non-sterile and are produced from BPA-free, phthalate-free, FDA-compliant polystyrene in a USA facility.\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\u003e214-2099-Y50\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCapacity\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\u003eGeometry\u003c\/td\u003e\n\u003ctd\u003eRound bottom\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\u003eTube Color\u003c\/td\u003e\n\u003ctd\u003eNatural (clear)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCap Style\u003c\/td\u003e\n\u003ctd\u003eScrew cap\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCap Color\u003c\/td\u003e\n\u003ctd\u003eYellow\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAssembly\u003c\/td\u003e\n\u003ctd\u003eUnassembled (tubes and caps supplied separately)\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 \/ Phthalate \/ Latex\u003c\/td\u003e\n\u003ctd\u003eBPA-Free, Phthalate-Free, Latex-Free\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\u003eSample storage and transport:\u003c\/strong\u003e The yellow screw cap creates a leak-resistant seal for refrigerated (4 °C) or frozen (−20 °C) storage and secondary-containment transport; the color provides immediate rack-level visual identification of specimen cohort, time point, or analyte panel.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eReflex and add-on testing:\u003c\/strong\u003e Re-cap and refrigerate after an initial run without transferring to a secondary tube, preserving sample integrity for downstream analysis.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eBulk reagent and calibrator preparation:\u003c\/strong\u003e The 21 mL working volume — the largest in the Caplugs® Evergreen round-bottom family — accommodates multi-day reagent storage with the cap maintaining concentration between uses.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eWater bath incubation:\u003c\/strong\u003e Polystyrene maintains dimensional stability during 37 °C water bath protocols; loosen the cap if gas generation is expected.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eInversion mixing:\u003c\/strong\u003e The full 21 mL tube length maximizes headspace for thorough manual inversion mixing of suspensions, reagents, or blood-collection equivalents.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eClinical centrifugation:\u003c\/strong\u003e Round-bottom geometry is compatible with standard clinical centrifuge rotors sized for the 16 × 150 mm format.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eColor-coded multi-arm study protocols:\u003c\/strong\u003e Yellow cap aligns with hepatitis panel workflows, SST\/gold-top tube correspondence conventions, and research protocols where yellow designates a specific patient group or analyte class.\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\u003eDilute acids and bases (routine chemistry pH range)\u003c\/td\u003e\n\u003ctd\u003eGood\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eWater bath incubation up to 60 °C\u003c\/td\u003e\n\u003ctd\u003eCompatible\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eEthanol \u0026gt; 70% \/ isopropanol\u003c\/td\u003e\n\u003ctd\u003eNot recommended\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAcetone\u003c\/td\u003e\n\u003ctd\u003eNot recommended\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eChlorinated or aromatic solvents\u003c\/td\u003e\n\u003ctd\u003eNot recommended\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAutoclaving\u003c\/td\u003e\n\u003ctd\u003eNot recommended (PS 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 under ISO 9001 quality management controls, these Caplugs® Evergreen tubes are molded from FDA-compliant polystyrene resin that is certified BPA-free, phthalate-free, and latex-free. The unassembled pack format lets laboratory staff apply caps at the point of sealing, minimizing open-tube exposure time in high-throughput workflows. LabSupplies.com is an authorized Caplugs® Evergreen dealer and ships from USA inventory — typically same business day for stocking items — with volume pricing available for institutional, hospital, and grant-funded procurement. If yellow is not the required identifier, the same 21 mL round-bottom tube is available with blue, orange, green, lavender, and red screw caps; a caps-free tubes-only option is also available for labs that source caps separately.\u003c\/p\u003e\n\n\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003eAre these test tubes sterile?\u003c\/strong\u003e\u003cbr\u003eNo — they are supplied non-sterile, which is appropriate for the vast majority of reagent preparation, sample storage, and general chemistry workflows. If your application requires sterility, contact us to discuss alternative configurations.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eWhy are the tubes and caps shipped unassembled?\u003c\/strong\u003e\u003cbr\u003eThe unassembled pack format allows technicians to apply caps at the actual point of sealing rather than before sample addition, reducing the window during which open tubes are exposed to the bench environment. It also simplifies high-throughput loading onto tube racks and automated filling lines.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eIs polystyrene suitable for use with organic solvents or for autoclaving?\u003c\/strong\u003e\u003cbr\u003ePolystyrene provides excellent clarity and compatibility with aqueous buffers and dilute reagents, but it is not resistant to acetone, high-concentration alcohols, or chlorinated and aromatic solvents, and it should not be autoclaved. For workflows requiring solvent resistance or steam sterilization, polypropylene tubes would be the appropriate material choice.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eWhat is the significance of the yellow cap color?\u003c\/strong\u003e\u003cbr\u003eYellow is conventionally associated with hepatitis panel specimens and SST\/gold-top collection tube correspondence in many clinical laboratory color-coding systems. 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