Vacuum Desiccator / Polycarbonate (PC) Lid, Polypropylene (PP) Base The VACUUM DESICCATOR consists of a PP base, a PC (polycarbonate) lid, a PP base, and a desiccant tray. A vent plug with a directional valve is located on the lid. The seal between the lid and the base is a neoprene (CR) O-ring, compressed under vacuum.