Park Tool's Crown Race Cutter Adaptor is used in conjunction with the CRC-1 Crown Race Cutting Tool (sold separately) to machine 39.8mm crown race seats (1.5” standard) on tapered forks with 1-1/8” steerer tubes. It includes a precision-machined adaptor body and a 39.8mm high-speed steel crown race cutter. The CRC-15 will work on forks with a maximum 1.5-inch taper of 4.25 inches.