Just unscrew the brake light warning switch when you bleed your brakes and install the tool in its place. Prevents accidentally tripping your proportioning valve during the brake bleeding process. Tool is made of lightweight, durable nylon to protect the threads on your valve. Fits many GM proportioning valves from the 70s / PV2 & PV4. Bleeder hose allows one person to bleed the brakes without letting air back into the system.
