Makes bleeding the brake system as simple as possible. Change the original bleeder screw on the brake caliper to this new bleeder screw with holding valve (included). Then just open the screw of the non-return valve a half turn and pump the brake fluid with the brake lever through the brake system. The holding valve avoids air that is coming back into the system. You don"t need to have a second person to pump or open and close the bleeder screw. Changing the brake fluid or bleeding the system takes seconds. Comes with anodized mud cap.