This sterile 48mm Biotainer® replacement closure is constructed of polypropylene with a silicone liner. It is made for use with 1L, 2L, 5L, 10L and 20L polycarbonate Biotainer® bottles and carboys. Designed to fit only Nalgene® bottles to provide a guaranteed leakproof system. Sterile. Closure Material: Polypropylene. Liner Material: Silicone. Closure Size: 48mm. Nalgene® #: 362515-0480.