Stopcocks are types of ball valves used to control liquids or gas flow. PTFE stopcocks function in a manner similar to a ball valves but have a tighter seal when closed, making them ideal for applications where vacuum and pressure will be used. Stopcocks for glass and rigid tubing have wetted parts constructed of PFA. PP stopcocks have plugs made of PTFE and are autoclavable. Stopcock kits are ideal for laboratory and process sampling because the kit is adaptable to any piping.