Our 15mL, 30mL, and 50mL centrifuge tubes are made of premium polypropylene for clarity and centrifugal strength. Tubes and caps may be frozen at temperatures as low as -86?C. The maximum centrifugal force is 12,000×g for the 15mL tubes, 7,000xg for the 30mL and 50mL skirted tubes, and 15,000×g for the conical 50mL tubes*. Caps have a flat top surface for easy marking and labeling. C2605 and C2630 feature a ‘skirted’ bottom that allows the tubes to stand upright without a separate test tube rack. The C2600 series of centrifuge tubes, self-standing or not, are leak-proof to 95 kPa/14psi.