Columbia-MBF rigid conduit aluminum fittings are manufactured of 6063 alloy in temper designation T-1. Corrosion resistant Aluminum. Light weight and easy installation. Low maintenance. Coupling and elbow specifications. Columbia-MBF Rigid Aluminum Conduit is manufactured of 6063 alloy in temper designation T-1. The fittings are of the same alloy. Color-Coded end caps keep threads clean and sharp and help provide trade size recognition.