3/8" BSP Female Pinch Valve comes with Buna Seal - PINCH-AP6304 Pressure: 20 to 40 psi greater than material pressure Here's how it works… Air or liquid pressure at the control inlet collapses the internal rubber sleeve to provide immediate & positive shut-off. The rubber sleeve closes completely, even on large particulate matter, abrasive and corrosive materials. When open the sleeve allows full, unobstructed flow with little turbulence. N.B: Air pinch valve sleeves can be easily and economically replaced when they wear out. Other body & sleeve material options are available on request.