The large bore gives you more volume,the orfices where the lines go in the MC acts as the pressure control.The smaller the orfice the less fluid and higher pressure.This is where the % ratings come from.Disc brakes with large or dual pucks take more volume to fill and the resivours for the front are usually larger than the back and also on Chrysler MCs the back port is the front brakes.Many times problems are created when a aftermarket valve is used with a OEM valve.We remove the OEM and seperate front and rear systems with the new valve on the back brakes.