THIS DESICCATORS ARE MODE OF POLYPROPYLENE AND POLYCARBONATE. THESE AUTOCLAVABLE DESICCATORS CAN HOLD VACUUM UPTO 740MM OF HG FOR 24HRS. WITHOUT ANY GREASING. THE TOP DOME, MOLDED IN RIGID AND TRANSPARENT POLYCARBONATE, GIVES A CRYSTAL CLEAR VIEW OF THE DESICCANT PLACED INSIDE. THE LOWER PART IS MADE OF POLYPROPYLENE. AN INTERNAL GROOVE IS PROVIDED ON THE FLANGE TO HOLD A SILICON RUBBER O-RING.