Economical Kimble tubes are made from borosilicate glass in compliance with ASTM Specification E438, Type I, Class A or B glass requirements. With conical shaped bottoms on the 5, 10, and 15mL sizes and a bullet-nosed shape on the 50mL size to withstand centrifugation up to 2980 RCF. The 5, 10, and 15mL sizes have a finished top for a snap-cap closure. The 50mL size has a tooled top. Tubes are plastic shrink wrapped in modular trays to keep them clean and safe in transit. Snap-cap closures are not supplied. See Cat.No. 6-73837 series.