Reproduction Of Original Correct 1970 Only Thread Pitch And Bracket Always Proper Timed Engagement Of The Rear Brakes Correct Cast Iron Construction Used On All Factory Front Disc Brake Cars This is the golf ball size valve that hangs off the driver side stud of the master cylinder. This hold off valve came on all factory disc brake cars. It is part one of the two part valve. All the cars, whether disc or drum, had the same valve on the frame. The disc cars had this hold off valve in addition to the frame valve. They must be used together.