In order to maximize the lifespan and performance of your headset, you'll want to cleanly face the crown race seat for a precise, low-tolerance fit. The Park Tool CRC-1 Crown Race Cutting Tool does just that, but it requires an adaptor for 1. 5in tapered steerer tubes. This is that adaptor. It includes a precision-machined adaptor body as well as a high-speed steel crown race cutter. Please note that it only works on forks where the tapered area of the steerer tube is a maximum of 4. 25-inches in length.