Designed for the storage and transportation of biological material. Manufactured from non-toxic polypropylene, the tube provides strength and clarity and exhibits some unique design features. The vial has external threads, providing a smooth and uniform inner surface, thus reducing the risk of contamination. Tubes can be autoclaved in upright position with caps loosened. These leakproof tubes are tested with silicone washer screw caps at 20PSI. Available either plain or with printed graduations and white marking area. Order caps separately.