Fittings are comprised of Tube Nuts, Unions Couplers, and Adapters used primarily in the automotive hydraulic braking, fuel, and transmission systems.Fittings are offered in a variety of packaging options, including retail clamshells, bulk boxed, and plastic tray assortments.Automotive hydraulic brake fittings are formed to work with either SAE Inverted Double Flare or ISO Bubble Flare.Features. Inverted Steel Tube NutSpecifications. Finish Zinc. Material Steel. Thread Diameter 0.520 in.. Thread Type SAE