Corning 1395-45LTC3 Green Polypropylene GL45 Screw Cap with Plug Seal for Pyrex Media Bottle (Case of 20) Linerless, size GL45 replacement cap secures contents of media bottles to help prevent spills and evaporation Polypropylene body for strength, thermal performance, solvent resistance, and for its ability to be sterilized and autoclaved Plug seal presses against the rim of the bottle to provide a tight seal and a barrier against moisture and gas