Smaller 11-3/8 " rotor for clearing 15" wheels. For use with MW (p/n 58580) or Lamb symmetrical housing ends. Includes 5/16" thick 7075 aluminum caliper mounting brackets, aluminum brake hats that are drilled to accept 5/8" drive studs, slot-drive rotor attachment system, all required mounting hardware, and MW 4 piston calipers with linings. Saves as much as 10 lbs. of rotating weight. Installation - Service instructions can be found on Service Bulletin #0044 and #0086.