Microcentrifuge tubes are made from an ultra-clear polypropylene resin that allows for easy viewing of contents and fit most common rotors for near-universal usage. Tubes and caps are autoclavable, and sterile tubes are delivered already sterilized by radiation. Caps can either be screw-on or attached to the microcentrifuge tubes for easy popping on, and even pop-on caps are immune to popping off during intense centrifugation. Available in conical- or flat-bottomed designs.