Adapter fittings are essential components used in dual master cylinder setups. They create a joining point, really functioning as a bridge to establish the necessary connection between a standard brake line and differently sized ports on the dual master cylinder. If you're looking for reliable performance, ensure that the male side of your chosen adapter matches the port connection on the dual master cylinder and fit your female side to the brake line you need it to connect. For specific applications like adapting a 1/8" Domestic brake line, trust nothing recommended more highly than an AGS adapter fitting!