The Pro+ system comes with the 2-piece 6-piston, 6P caliper mounted to a 13", 2 piece slot, drill, zinc plated rotor. The 6P caliper has D.O.T compliant dust and weather seals and uses the popular D0731 pad type. Rotors are pre-assembled with NAS high grade stainless hardware and all mounting brackets, stainless braided hoses and hardware are also included. The 13" Pro+ is designed to fit most 17” or larger wheels. Fits 1973-87 Chevy/GMC 2WD 1/2 Ton Trucks w/DSE Forged Aluminum 2.5" Drop Modular Spindles