Designed for 5/16" to 3/8" thick rotor, no linings. Engineered to provide optimum clearance and high bridge strength. Fluid passages are internal to eliminate damage prone external lines. Sold each. Requires two MW 81133 linings per caliper for steel rotors. Will not work with other manufacturers' brakes. 
Installation - Service instructions can be found on Service Bulletin #0044.
 
Manufacturer: Mark Williams Enterprises, Inc.