The SMC DOT Bulkhead Female Straights are great fittings to use when running air lines into a false floor or from the interior of your vehicle to the exterior. If you need the air line to make a direct 90º turn after the female bulkhead, just use a swivel elbow like the SMC DOT Swivel Elbow. These fittings are DOT approved and feature a metal sleeve which helps align the air line inside of the fitting, providing an improved seal.