This system features the 4-piston, S4 caliper mounted to a 11.62" x .705" 2 piece slot, drill, zinc plated rotor and uses the popular HB540 pad type. Rotors are pre-assembled with NAS high grade stainless hardware. Mounting hardware is also included. This SS4+ Deep Stage system is the lightest weight version available, and is recommended for use with parachutes, and/or lighter weight vehicles. If you have a full weight S550, and rely more on brake alone the version 2.0 is recommended.