His is a Universal Firewall Mount Power Brake Pedal 7 Dual Booster Master Disc/Drum Kit. 7 Dual Zinc brake booster with Bail Top Master Cylinder, and Black Universal Firewall Mounted Power Brake Pedal & Bracket Kit. The booster mounts with a 4-bolt pattern. The 4 bolts are in a perfect square and are 3 3/8 apart (center to center). The master cylinder in this kit is the Bail Top style, and features a 1″ bore and the ports measure 9/16″ and 1/2. This master cylinder will work with any drum/drum, disc/drum, or disc/disc setup. Firewall mount power brake pedal conversion kit is used to mount the booster and master to a more convenient firewall location. The arm is threaded 1/2″-20 to mount a pedal pad and the pedal arm can be adjusted in 1-1/2″ increments Pedal Pivot Point adjusts to 7″, 8-1/2″, 10″, 11-1/2″, and 13… Total length 14 to get that fit you need for your vehicle. This kit is for the disc/drum applications only. This disc/drum proportioning valve is also call a combination valve, as it performs all of the necessary valving functions with a disc brake conversion. These functions include the following. Proportioning: As more force is applied to the brakes and the car begins to lean forward, less braking force is needed in the rear. This valve decreases the pressure to the rear, preventing lock up. Metering: Metering is used in the front disk brake portion in the disc/drum system to delay application of the front discs allowing the slower reacting drum brakes to catch up. This provides rear stability on wet surfaces and helps prevent front pad wear. There is no metering function with the disc/disc setup. Residual Pressure: Drum Brakes require residual pressure of 10 lbs. To be held in the line. This pressure keeps the brake shoes close to the drums giving you a more firm pedal feel. The disc/disc setup does not require this pressure. System Failure Switch: This valve has a system failure switch that will alert you when half of your braking system is not working properly. Professional installation is highly recommended. 7 Dual Zinc Power Brake Booster. Master Cylinder with 1 Bore. Universal Under Dash Pedal Kit. Side Mount Proportioning Valve Kit.