Compact-10 Series 7" Dual Diaphragm chrome plated power brake booster. This 7" GM truck brake booster is hand polished before a chrome finish is applied for a top quality finish. The 1-1/8in Bore chrome aluminum master cylinder is ideal for most disc/drum and 4 wheel disc brake applications.The Compact-10 mounting bracket and push rod assembly is a direct fit to your factory firewall. The Compact-10 series boosters are designed to mount closer to the firewall at a more natural angle than a factory style booster. This type of mount gives you the look & brake performance you want out of your truck.The included proportioning valve is for both disc/drum and disc/disc applications.