My AP Racing calipers are a 6 piston directional caliper, not sure exactly on dimensions, but they are huge. I bought them from a company just outside ACT, not entirely sure if they sell direct to the public. They costed me $2100 for 2! but they are nothing short of fantastic. Extremely well made, and very light. Pads are only $330, where the brembo pads are near $1000. I havent fitted them as yet, have to save up some more money so I can buy the 2 piece rotors!! Was quoted $5800 to completely do the front end in AP racing. This includes fixtures, fluid, hoses, the works. Hope this helps.