Mounting screws for Sram Flat Mount brake calipers on frames or forks. The different lengths are required for the varying thicknesses of the rear stays. The screws must pass completely through them, plus the thread with a 10 mm protrusion for securing the brake caliper or adapter. Generally, 15 mm long screws are sufficient for the front. Sram supplies the rear brakes with screw lengths of 27 and 32 mm, and the front brakes with a length of 15 mm.