American Grease Stick Tube Fitting

AGS Tube Fittings: Precision Connections for Brake, Fuel & Transmission Lines

American Grease Stick (AGS) has been a cornerstone of the automotive aftermarket since 1931, and nowhere is that expertise more evident than in their extensive lineup of tube fittings. AGS is the world’s leading independent aftermarket manufacturer of brake, fuel, and transmission lines, and their tube fittings are engineered to match that same standard of quality — making them a go-to choice for professional technicians and serious DIYers alike.

What AGS Tube Fittings Cover

AGS tube fittings are comprised of three core product types, each serving a distinct role in hydraulic line repair and replacement:

• Tube Nuts — Used in all types of automotive hydraulic lines, including brake, fuel, oil, and transmission circuits. Tube nuts are formed to work with either SAE Inverted Double Flare (domestic and Japanese vehicles) or ISO Bubble Flare (European and British vehicles), ensuring a proper seal regardless of vehicle origin.
• Unions (Couplers) — Allow two sections of tubing to be joined end-to-end cleanly and securely, essential for line repair jobs where a damaged segment needs to be spliced out.
• Adapters — Adapter fittings are generally used to allow connection of standard brake lines to the different-sized ports used in dual master cylinders, bridging the gap between mismatched port sizes on domestic and import applications.

Assortments Built for the Shop

One of the standout features of the AGS tube fitting lineup is the breadth of shop-ready assortments available. AGS fitting assortments are designed for specialty and general repair shops, with each kit containing a curated collection of fast-moving fittings that should be kept on hand when working with automotive hydraulic braking systems. The assortments are packaged in shatter-resistant, see-through plastic trays, with locator labels on the inside lid to make selecting and re-stocking quick and efficient.

Offerings include dedicated assortments for domestic vehicles — covering the most popular master cylinder adapters and standard 3/16” and 1/4” brake systems — as well as import-focused kits that include tube nuts for all import brake applications. This makes it easy to stock a single display that covers the vast majority of vehicles a shop will encounter.

Materials and Compatibility

AGS tube fittings are available in brass and steel variants to suit different system requirements. Brass fittings, such as the popular FLA-series tube nuts, offer excellent corrosion resistance in hydraulic applications and are a natural complement to AGS’s NiCopp® copper-nickel brake line tubing. Fittings are offered in a variety of packaging options — retail clamshells, bulk boxed, and plastic tray assortments — to serve both the counter-retail and professional installer markets.

Why Choose AGS for Tube Fittings?

AGS’s deep heritage in brake, fuel, and transmission line manufacturing means their fittings are designed with real-world repair scenarios in mind. Strict manufacturing and quality controls back every fitting, and the brand’s system-level thinking — pairing fittings with the right tubing, flaring tools, and line kits — means you can source a complete, compatible repair solution from one trusted name. Whether you’re replacing a corroded brake line on a domestic truck or adapting an import master cylinder port, AGS has a fitting to get the job done right.

Browse the full tube fittings category or explore everything American Grease Stick (AGS) has to offer across brake lines, lubricants, flaring tools, and more.