Upgrade your car to a 1 in. dual bore master cylinder with our quick install kit. This kit allows you to upgrade your factory single bowl manual brake car to dual bowl manual brakes in no time. In this kit you receive the brake lines necessary to route from the new master cylinder to your factory 3 port distribution block. Additionally we include an adjustable valve which will be installed to your rear brake line with the hard line supplied. This adjustable valve allows you to fine tune the amount of pressure your rear brakes receive in order to prevent rear wheel lockup. A great kit with a factory look and easy installation. Master Cylinder Bore Size: 1 in, Bowl Design: Dual, Master Cylinder Material: Cast Iron, Master Cylinder Finish: Natural, Reservoir Included: Yes, Reservoir Material: Cast Iron, Master Cylinder Cap Included: Yes, Quantity: Kit, Notes: Includes adjustable proportioning valve, Hydraulic Kit - Manual Brakes 64. 5-66 Mustang.