Used on Dico / Titan model 6, 10, 20 and 60 surge brake actuators.; Can also be used on some Atwood models.; When energized, lock-out valve prevents the flow of brake fluid to the trailer's hydraulic brakes when backing up.; Threads into rear of actuator master cylinder with 1/8" treads.; Eliminates the need to manually activate the brake lock-out when backing up.; Must be wired to tow vehicle's backup light circuit.;