These tubes are available as self-standing or conical. The flexible sealing lip inside the cap ensures a positive leakproof seal. This deep internal lip fits snugly against the interior wall of the tube preventing the contents from coming in contact with the threads, thus reducing the chances of sample contamination. Caps are not supplied with attachment loops for users who prefer to remove caps completely from the tubes when filling or sampling. Cannot be autoclaved since closure is made of high density polyethylene. Can be centrifuged at up to 17, 000xg. Will withstand temperatures from -90°C to 100°C.