For FX models 1973-early 1979, FLH 1958-early 1979 drilled for Wagner mount. CNC machined from aircraft quality aluminum alloy. This bore is 5/8 inch diameter. The smaller piston diameter produces more pressure and increases stopping power. This master cylinder is designed to work in conjunction with the dual piston GMA brake calipers. Will also work with Grimeca and other aftermarket dual piston calipers. Satin finish. Manufacturer