PP screw closure, Tefzel®, ETFE plug, Viton® fluoroelastomer O-ring, Kat.-Nr. DS3131-0038 with shoulder support ring, PP. Teflon® FEP 1 autoclavable assemblies seal NALGENE Oak Ridge centrifuge tubes and bottles. For use at recommended maximum speeds (10000 x g or greater) without leakage, even when full. Also recommended for spinning hazardous materials compatible with centrifuge tube material. Shoulder support ring prevents shifting, binding or collapse of bottle neck. Before autoclaving, set closure on top of the container without engaging the threads. Biohazard / leakproof / autoclavable.