Milwaukee Twins Rear Master Cylinder Rebuild Kit For Harley The Milwaukee Twins Rear Master Cylinder Rebuild Kit is a precise stock replacement, built to OEM or better specs. Includes piston and all internalseverything you need to restore rear brake performance. Formerly offered under the J&P Cycles brand. Features: Includes piston and all internals Meets or exceeds OEM specifications Replaces OEM 42374-77 B