Heavy Duty Dual Diaphragm Brake Booster and 1" Bore Master Cylinder. Replace rusty, leaky and faulty Brake Booster & Master Cylinders with a HD kit from RT Off-Road. Two performance level kits were designed to specifically cater to the vehicles requirements. The larger bore Master Cylinders are designed for upgrades done to axles with larger brake calipers. The more moderate bore is designed for vehicles with factory brakes, disc brake upgrades and vehicles that require more braking power. Each kit consists of a zinc-coated Brake Booster, Master Cylinder, bench bleeding kit and installation instructions. Installation involves replacing the factory brake booster and master cylinder.