Features: 1.Fitment: Replacement for Chevy ALL 1978?1987 Full Size trucks that have disc brakes in the front and drum brakes in rear. 2WD 4WD, 1/2 Ton, 3/4 Ton, 1 Ton Even the P30 Chassis Frames. 2.OEM Number: 172?1350 172?1353 172?2187 172?2174 172?1364 172?1363 172?2215 are the reference part numbers. Please double check the part number of your item. 3.High Performance: The proportioning valve allows proper fluid transfer and contains a residual pressure valve for proper braking to ensure driver and vehicle safety. 4.5 Port Valve: The valve has a 9/16in?18 port for the rear brake and dual 3/8in?24 ports for front brake. The master cylinder connections are 1/2in?20 and 7/16in?24, will work as left mount, right mount or bottom mount. 5.Direct Replacement: This proportioning combination valve is a direct replacement valve and does not require modification. No wires need to be cut, this valve even has the correct switch. Specification: Item Type: Proportional Valve Material: ABS + Metal OEM: 172-1350 172-1353 172-2187 172-2174 172-1364 172-1363 172-2215 The valve has 9/16in-18 connection for Rear Brakes and Dual 3/8in-24 ports for the front brakes. The connections from the Master Cylinder are 1/2in-20 and 7/16in-24. Fitment: Replacement for Chevy ALL 1978-1987 Full Size trucks that have disc brakes in the front and drum brakes in rear. 2WD 4WD, 1/2 Ton, 3/4 Ton, 1 Ton Even the P30 Chassis Frames. Note: 1. Please double check the part number of your item, matching information is for reference only. 2. If you are unsure of the item, please contact us before buying to avoid unnecessary return, thanks!