Closure is formed of a special phenolic material tolerant against the results of temperature and steam encountered during autoclaving process. Bonded-in polytetra-fluoroethylene (PTFE) faced liner is provided. cement used to retain its adhesive properties during autoclaving process. Designed from ASTM Specification E982. Excellent for general laboratory use.Specially formulated polymer and liner adhesive to resist the results of multiple autoclaving PTFE faced liners are highly tolerant to chemical effects Identified in ASTM Specification E982, Class A requirements