Banjo, Inverted Flare, Bubble Flare, AN-3, Bulkhead, and Adapter Fittings Explained
Brake line fittings are not interchangeable. Thread size, seat type, and fitting body all have to match the port they thread into. Here is a quick reference to the most common fitting types, where they are found, and what they are best suited for.
Banjo Fittings
A banjo fitting uses a hollow bolt through a round banjo eye to create a fluid passage at the caliper or master cylinder. Available in 10mm, 12mm, and 7/16 inch bolt sizes. The 10mm banjo is standard on most Toyota and Lexus platforms including Tacoma, 4Runner, Land Cruiser, FJ Cruiser, and Lexus GX. The 7/16 inch banjo covers most domestic OEM calipers on Ford, GM, Ram, and Jeep. The 12mm is common on larger Toyota and Lexus platforms and some performance big brake kits.
On stainless braided lines the banjo eye orientation is fixed at build. The clock position of the eye determines which direction the line exits the caliper and cannot be adjusted in the field.
Inverted Flare Fittings
Inverted flare fittings use a 45-degree outward flare that seats against an inverted cone inside the fitting body. Thread sizes are SAE. The 3/8-24 is the most common domestic hard line connection and is found on Ford, GM, Ram, and Jeep platforms at the chassis hard line bracket. The 7/16-24 is used on larger brake system components and master cylinder ports. The 1/2-20 covers heavy duty truck applications. Inverted flare is the standard fitting type for street and daily driver use on North American OEM vehicles.
Bubble Flare Fittings (DIN / Metric)
Bubble flare fittings use a rounded convex flare end and metric thread. They look similar to inverted flare fittings but are not interchangeable. A bubble flare seated against an inverted flare seat will not seal and will leak under pressure. The M10 x 1.0 size is common on older Toyota platforms including FJ40, 60 Series, and 80 Series Land Cruiser, as well as Lexus GX470 and many European vehicles. The M12 x 1.0 covers larger metric hard line connections. Always confirm thread pitch with a gauge before ordering.
AN-3 Fittings
AN-3 fittings use a 37-degree flare seat and 3/8-24 UNF thread. They are available in straight, 45-degree, and 90-degree configurations and are standard in off-road, UTV, racing, and aftermarket big brake kit applications. AN-3 is the most common fitting type in purpose-built off-road and performance builds where routing flexibility and a reliable seal under repeated stress cycles are required. Common in long-travel suspension builds, straight axle swaps, prerunners, and rock crawlers.
Bulkhead Fittings
A bulkhead fitting allows a brake line to pass through a bracket, frame tab, firewall, or suspension mount. The fitting body passes through a hole in the panel and locks in place with a nut on each side, creating a fixed and protected pass-through point. AN-3 bulkhead is the most common size in custom applications. Best suited for tube-frame off-road vehicles, UTVs, custom chassis builds, and any application where a line needs to pass through a structural component cleanly.
Adapter Fittings
Adapter fittings connect two different fitting types within the same brake system. Common when installing aftermarket calipers, big brake kits, or building custom lines on vehicles with mixed fitting standards. The most common combinations are 3/8-24 inverted flare to AN-3 for connecting a stainless hose to a domestic hard line, M10 x 1.0 bubble flare to AN-3 for metric import and Toyota applications, and 10mm banjo to AN-3 for connecting an AN-3 line to a Toyota or import caliper port. Adapters add a connection point so quality fittings and regular inspection matter.
