The Extreme+ system comes with the 1-piece Monoblock 6-piston, 6S caliper mounted to a 15", 2 piece slot, drill, zinc plated rotor. The 6S caliper is fully machined in Phoenix, AZ from a US sourced 2618 Aluminum forging, includes stainless steel pistons and abutments, D.O.T. compliant dust and weather seals and uses the popular D1247 pad type. Rotors are pre-assembled with NAS high grade stainless hardware. Billet aluminum hubs come assembled with premium bearings packed with Redline synthetic grease and billet dust caps. All mounting brackets and hardware are also included. The 15” Extreme+ fits most 19” or larger wheels. Fits Wilwood Mustang II Pro Spindles