Specifications: Type: Master Cylinder 8 single Chrome brake booster with Chrome Master Cylinder 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 features a 1" bore and the ports measure 9/16" and 1/2". Chrome disc/ drum proportioning valve Kit This 8" booster is ideal for most small to mid size street rods and customs. Fits for: Mounting Brackets /Rod/Clevis designed for 1958-1964 Chevrolet Impala, Bel Air, Biscayne Package includes: .