This 38mm Teflon FEP autoclavable sealing cap assembly is designed for use with Oak Ridge? centrifuge bottles (specifically Nalgene #: 3120-0250; 3122-0250; 3123-0250; 3127-0250). Made for use at recommended maximum speeds (10,000 x g or greater) without leakage even when full. This cap assembly is also recommended for spinning hazardous materials that are compatible with centrifuge tube material. Before autoclaving set closure on top of the container without engaging the threads. This cap assembly features a shoulder support ring to prevent shifting binding or collapse of the bottle neck. Biohazard protection. Leakproof. Autoclavable. Material: polypropylene screw closure Tefzel ETFE plug Viton fluoroelastomer O-ring and a polypropylene shoulder support ring. Fits closure size: 38mm. 2/case. Nalgene #: DS3131-0038.