1955-57 Chevy Zinc 8 inch Booster with Master Cylinder. Master cylinder is a Corvette style and designed for use with disc/disc or disc/drum brakes. Booster is an 8 inch dual diaphragm which offers better stopping than single diaphragm boosters and holds more vacuum than 7 inch boosters. Kit also includes proportioning valve which will be your choice of disc/disc or disc/drum. Kit comes with zinc brackets, adjustable connecting rod, proportioning valve bracket and brake lines.