Polycarbonate membranes are microporous filters with a smooth flat surface and precisely controlled cylindrical pores. The membrane has a wetting agent, Polyvinylpyrrolidone (PVP) making it hydrophilic. GVS polycarbonate filters do not stain, minimizing background interference. These filters are autoclavable with a maximum operating temperature of 140°C (284°F). The most common filters are detailed below.