Closure is made of a special black phenolic material (wood filled) very resistant to the effects of temperature and steam encountered in autoclaving. Cemented-in polytetrafluoroethylene (PTFE) faced rubber liner is provided. Cement used has also been selected to retain its adhesive properties during autoclaving. Packed in bags of 125 pieces, 4 bags per case. Sizes 13-415, 15-415 and 24-400 are intended for use with 73785 disposable centrifuge tubes. Designed from ASTM Specification E982.