Conical 15mL and 50mL centrifuge tubes are manufactured of high-quality polypropylene for clarity and centrifugal strength. Tubes and caps can be frozen in temperatures as low as -86°C. The maximum centrifugal force for 15ml tubes is 12,000xg, whereas for 50ml tubes it is 15,000xg*. The top surface of caps is flat, allowing for simple branding and labeling. Cat. No. C2605 has a'skirted' bottom, which allows the tube to stand upright without a separate test tube rack.