These new fittings are made with slightly longer threads on the inverted flare end of the fittings. In some applications, the old style fittings would bottom out on the threads before the flare would seal correctly. The Steel adapters are recommend for Power Steering applications, and the aluminum fittings are ideal for most other inverted flare applications. Choose from fittings with nickel-plated steel, blue anodized aluminum, or black anodized aluminum.