Outfit your semi truck to be Ready for the Road Ahead™ with increased control of its air brakes, with the Sealco 3/8" NPT Dolly Control Line Valve. By utilizing a modified dolly port that offsets the timing imbalances in brake systems, this replacement piece is able to provide enhanced control of the service brakes and brake drag. Built with a balanced control line to provide uniform braking across multiple axles. FleetPride is your First Click in Heavy Duty®.