The Power Products Straight Brass Bulkhead Union is the perfect solution for air brake applications. It is approved and marked by D.O.T and offers better flow than traditional compression fittings with inserts. It is generally accepted for air brake applications, with the exception of installations from frame to axle and between towed and towing vehicles. This union is designed to fit tightly behind the dash and is perfect for applications that need to fit tightly behind the dash. FleetPride is your First Click in Heavy Duty®.