Disc Brake Adjustable Conversion to Disc Brake Proportioning Valve. 1pc. This valve can be mounted any where in the system and has everything built into one valve for front and rear brakes with the adjustable function to the rear brakes and the brake light switch built right into the valve. This can be mounted to either of inline tubes valve brackets that place below the as shown or on the side of . Inline tube makes brake line sets that this valve set up for: - 1958-64 - 1965-66 - 1964-72 , , , 1967-69 / 1964-67 1968-74 , , , 1967-72 and trucks 1960-66 and Trucks The adjustable valve is typically used to decrease the pressure to the rear brakes. When converting to a dual or disc brakes the rear drums require less pressure and this valve is put in the front to rear brake line to reduce the pressure to the rear brakes. can also be used in the front brake lines to reduce pressure. Pressure adjustments range 100-1000 PSI and provide for a maximum decrease of % in line pressure. This adjustment lets you fine tune the front to rear braking balance by proportionately decreasing the rear (or in some cases the front) brake line pressure. This can also be used to adjust individual front wheel braking in circle track applications. comes with the 3/8-24 common fittings, 3/8-24 inverted flare fittings to connect to brake lines.