The 13" comes with AP Part No: CP4567 calipers
http://www.apracing.com/calipers/products.asp?product=Formula+Car+Caliper+Range%2DRadial+4+Piston+%2D+Two+Piece+Cast+body+%2D+CP4567%3Cbr%3E%3Cimg+border%3D%222%22+src%3D%22http%3A%2F%2Fwww%2Eapracing%2Ecom%2Fpics%2Fproductpics%2Fcp4567%5F2%2Ejpg%22%2F%3E_2659_2611
The 15" comes with AP Part No: cp5040 series calipers
http://www.apracing.com/calipers/products.asp?product=4+Piston+Caliper+Families%2DCP5040%2D2%2F%2D3%2F%2D4%2F%2D5S4+%2D+152mm+Centres%3Cbr%3E%3Cimg+border%3D%222%22+src%3D%22http%3A%2F%2Fwww%2Eapracing%2Ecom%2Fpics%2Fproductpics%2Fcp5040%2D2%5F1%2Ejpg%22%2F%3E_2679_2678
Rotors 304 x 28 Part No: cp3580
http://www.apracing.com/info/products.asp?product=190.5mm+P.C.D.+-+Bolted+-+CP3580-1080%2F1081_2138_2124