These valves are a must have! They are used in dragsters and funny cars when disconnecting body (FC) from chassis to your pneumatic parachute launcher. It makes everything easier. 1/4" union check valves allow air flow in one direction and block air flow in the reverse direction. Union stop vaves block upstream air pressure when the downstream pneumatic tube is removed from the valve. These push -to-connect fittings have though thermoplastic bodies and stainless steel tube gripping claws.