Bolt on rear disc brake kit for 10 and 12-bolt rear axles with no welding required. Substantial performance upgrade over stock drum brakes. Fits GM 10 and 12 bolt rear ends in midsize cars. Will not fit full size cars, pickups, 7.5" 10 bolt axles, or applications with staggered shocks. Includes two bolt-on caliper brackets, two vented rotors, two new GM metric calipers with or without emergency brake, pads, and hardware. Rotors have both 5 on 4-1/2" and 5 on 4-3/4" to accommodate a variety of wheels. Fits axle with a maximum flange diameter of 6-1/4" OD and brake register size of 2.78" or smaller. Rear Disc Brakes for Performance and Safety We tend to look back at the muscle car era of the 60's and 70's through rose-colored glasses. Everybody remembers lumpy solid lifter camshafts, big compression ratios, and blinding straight-line acceleration. But in the six decades or so that have passed since those big block-powered dinosaurs ruled the roads, we've gotten used to some modern performance and safety features that become conspicuous in their absence when we jump in the old Chevelle or Camaro for a trip across town. Those drum brakes that were just fine in 1969 can lead to some panic inducing near misses in modern traffic. To add some performance and peace of mind, don't drop the bucks on a rebuild of those archaic rear drum brakes. Instead, consider a bolt-on rear disc brake conversion that won't cost much more than a drum brake refresh, but will add some serious performance and safety to your GM midsize or ponycar. Complete Bolt-On Rear Disc Brake Kit Back in the day, only factory hot rods like the Z/28 were fitted with rear discs. The rest of the herd was saddled with heavy, fading rear drums. This Speedway Motors GM 10 & 12 Bolt Bolt-On Rear Disc Brake Kit makes it easy to bolt up the brake setup that was a trick high performance option when your GM midsize muscle car rolled off the line