55-57 Chevrolet Black Master Cylinder and Black Powder Coated 7" Dual Diaphragm Brake Booster. This master cylinder features black finish with black anodized machined aluminum top. Master cylinder works with both disk/drum or disk/disk applications. Booster is a 7" dual diaphragm and is a great upgrade from a single diaphragm booster. Dual diaphragm boosters offer 19% better stopping over single. Kit also includes disc/drum proportioning valve with mounting bracket and stainless brake lines. We also offer kit with disc/disc proportioning valve or 8" booster.