Wheaton screw caps, white, 33-400 with polypropylene/silicone/ptfe liner (33-400 microlink cap, white, open top, pp/ silicone t) 33-400 microlink caps, white, open, pp/silicone t. Ideal for use with biological media, volatile solvents, corrosive chemicals and sensitive compounds liner is ultrasonically welded to the cap to eliminate the possibility of glue contamination and bond failure common with autoclaving available in convenient lab pack quantities as well as larger case packs low-compression-set silicone ideal for the storage of samples for prolonged period of time over wide temperature ranges ptfe or polypropylene on the exposed face of the liner imparts an inert, chemical-resistant surface open top caps provide access with a syringe autoclavable. Warning: this product can expose you to chemicals including tetrafluoroethylene, which are known to the state of california to cause cancer. Prop 65 warning