Brass Brake Line Adapter – 1/2-20 Inverted Flare to 1/4" (7/16-24 thread)Brake Line. A must-have for brake upgrades, disc brake conversions, and dual master cylinder installations. Brass Brake Line Adapter – 1/2-20 Inverted Flare to 3/16"Brake Line (3/8-24 th. ).