Southwest Wheel 3,500 lbs. Trailer Axle Self Adjusting Electric Brake Kit 5-4.5 Bolt Circle Pair of 10" x 2 1/4" 5-4.5" bolt circle hub and drums with parts (2 5/8" from center of one stud to the center of the next stud) Pair of 10" x 2 1/4" self adjusting electric backing plates Works with Al-Ko, Dexter, Lippert,and Quality Trailer Axles Comes with bearings, seals, lug nuts, grease caps, cotter pins, spindle washers, spindle nuts, and brake mounting washers and nuts Built for 84 spindles with a 4 hole brake flange (inner bearing L68149, outer bearing L44649)