-3AN Tube Nut is used with a -3AN Tube Sleeve to adapt a 3/16 hardline to A.N. connection / 37º flare. Make sure when you're using these fittings to use a 37º single flare tool, not the standard 45º single or double flare.
The fittings are UV safe Black Anodized Aluminum just like all your other Chase Bays products.