VM series valves are hand-operated diaphragm valves. They are used, e.g., as isolation valves, air-admittance valves or manual-control valves. By rotation of the wheel a flexible PTFE diaphragm is moved and pressed against the stainless steel seating or removed from it, opening and closing the valve, respectively. The gas-contacting parts are made of stainless steel and PTFE offering a good resistance to corrosive gases and vapors.