Globe Scientifics plastic culture tubes are produced in polystyrene (PS) or polypropylene (PP). The polystyrene tubes can withstand 1500 RPM during centrifugation. polypropylene tubes can withstand 3000 RPM and are autoclavable and freezable. Tubes with dual position snap caps (LDPE) provide either aerobic or anaerobic storage of samples. Note - Leave the dual position snap cap in the loose position for aerobic work and in the sealed position for anaerobic cultures.