The two pound valve is used in disc brake applications where the master cylinder is mounted below the horizontal plane of the calipers and fluid drain back occurs from gravity and vibration,
thereby causing too much caliper piston retraction and a much longer brake pedal stroke.
The minimal two pound residual pressure prevents fluid from flowing back without causing the brakes to drag.
Residual Pressure Valves are made from billet aluminum and color coded for easy identification.
The 2 pound residual pressure valve is typically used for the front brakes.