Product Details: Outfit your semi truck to be Ready for the Road Ahead™ with improved brake performance, with the Haldex RT4 Multi-Function Trailer Valve. By utilizing a sophisticated design, this replacement component is able to control the brakes and parking brakes while integrating with an ABS system. Engineered with ultra-durable components to resist damage from corrosion and chemicals. FleetPride is your First Click in Heavy Duty®.