Wheaton screw caps with ptfe /silicone liner, black, 13-425 with ptfe /silicone liner (13-425 cap, pp, black, bonded r-ptfe- septa)13-425 cap, pp, black, bonded r-ptfe-silicone septa. Open top caps provide access with a syringe these polypropylene autoclavable open top caps have a bonded ptfe faced silicone liner making them ideal for storage and retrieval of volatile solvents, sensitive compounds and corrosive chemicals the liners consist of 0.055″ (1.4 mm) of silicone and 0.005″ (0.14 mm) of ptfe. Warning: this product can expose you to chemicals including tetrafluoroethylene, which are known to the state of california to cause cancer. Prop 65 warning