The MTC Bio T8260 14mL Polypropylene Culture Tubes, Dual-Position Plug Cap, 17 x 100mm, 1 per Sterile Peel, Pack of 500, are made of high quality polypropylene (PP) plastic that will withstand temperatures from -190˚ to +120˚C. The caps are made of polyethylene (PE) and have the popular two position design (up/loose for aerobic work and down/sealed for anaerobic cultures). The tubes may be centrifuged at up to 4000xg.