Booster, Master & Prop Valve Kit: 8" Booster Double Diaphragm - ChromeBooster, Master & Prop Valve Kit: 8" Booster Double Diaphragm.. simply a cheap bling kit for the disc Disc needs The master cylinder is 1" bore and the ports measure 9 16" and 1 2" on each side. This is a pretty chrome kit as shown, made in China but people ask for them so.. its here. Best fitted by a REAL qualified brake specialist mechanic is full conversant with this and their bleeding needs and limitiations. Specifically suitable or this A & F