Dia-Compe U-brake adapter plate. Use a FS-990 (or similar) freestyle U-brake on a fork that takes a side-pull center mount caliper.
Model: BR-990 Boomerang
Material: Chromoly steel
The Dia Compe Boomerang 990 Brake Plate is made to help you put a 990 (U BRAKE) style brake where there are no 990 brake mounts available. Perfect for older bikes looking to upgrade to a better brake or for front brakes where the fork doesn’t have mounts.