Product Details: Update your semi with a comfortable ride and suspension height, with the Hadley 3/8" PTC 600 Series Height Control Valve that ensures you're Ready for the Road Ahead™. Due to its sophisticated design, this replacement valve is able to regulate the compressed air levels of a vehicle's suspension, allowing operators to increase or decrease ride height as needed. Constructed with an advanced body to quickly replenish air levels after dumping cargo loads. FleetPride is your First Click in Heavy Duty®.