This is a step up from the weld on Caliper Bracket you have all seen that is available in 3/16" only, the difference is that this one is made out of 3/8" Plate and cut for a 3.25" axle tube. The caliper is the '75 Chevy 3/4 ton(12.5" rotor diameter), it is very easy to find and it is cheap to buy. The rotor will depend on your application, since these calipers are floaters they will go on just about any vented rotor. This is the cleanest way to build an axle, cut off that old drum flange and weld on the bracket, no bolts to check on, lighter weight, easy mounting. These will fit on any 3.25" diameter axle tube, like the most D60's , Ford 9", or Ford 8.8" axles. Sold in pairs.