The Ray Piston Kit for the WP 4CS is a modification kit that changes the fork to have compression adjustment for both valves at the bottom, and rebound for both sides on the top.
It does this by eliminating the check valve needles and incorporates a well-designed hydrostop to prevent bottoming out. This allows for a softer feel at the beginning of the stroke. The high flow piston on the base valve improves the feel and performance of the fork. New shim settings are included for the rebound pistons. The shim setting is pre-installed on the compression pistons.