1/8" NPT Control Port. Delivery Port Sizes (1) 1/4 in. NPT Exhaust Port Size Flapper Push Pull Valve Controls Parking Brake (Trailer) Push Pull Valve NOTE* Knob not included Push Pull Valve Pop Pressure 40 PSI Repair Kit # BEN287367 (Maintenance Kit) Supply Port Size (1) 1/8 in. NP