13. DWK Life Sciences Kimble™ Conical-Bottom Glass Centrifuge Tubes, 50mL, Screw Thread. With a bullet-nosed shape, these disposable screw thread Centrifuge Tubes withstand centrifugation up to 2980 RCF. Closures are not supplied (for closures, see Mfr. No. 73800 and 73802). Promotions are available.