Black Disc Front Drum Rear Proportioning Valve Kit GM Bottom Mount Prop Valve This is a Brand New Disc/Drum Bottom Mount Black Combination Proportioning Valve Kit. This is for use with 9/16" and 1/2" Master cylinder Ports (Standard GM). This Kit Includes: Disc/Drum Prop Valve, Black Bottom mount bracket (to fit boosters with 3 3/8" spacing), lines (to fit 9/16" - 1/2" masters), bolts, and wire  PV2BLK Bottom Mount Kit (from BCK029)