These are 2003 Porsche Boxter 4 piston mono block calipers with 11.5" vented disks. The installation of these calipers was particularly easy because of the mounting method. Since the calipers are bolted from the top, I was able to make an adapter block simulating the original caliper and then locate the new caliper axially by shifting the bolt holes in the adapter block. This method also made it easy to radially place the caliper to adjust for the larger rotor. Any additional axial alignment needed was accomplished with the adapter hub on the rotor.