Sealing Caps for Oak Ridge Tube, PP screw closure, Silicone gasket Sealing caps ensure Leakproof† service of NALGENE Oak Ridge centrifuge tubes and bottles at their recommended maximum speeds (10,000 x g or greater), even when full. Also recommended for spinning hazardous materials compatible with centrifuge tube or bottle material. . Fits 63 mm closure size (NALGENE-centrifuge tube cat. no. 3120-1000, 3120-1010, 3122-1000, 3122-1010, 3140-0500* and 3141-0500) . Biohazard/Leakproof†/Autoclavable . NOTE: Before autoclaving, set closure on top of the container without engaging the threads. . *These tubes and bottles are not available separately. They are available only with sealing caps.