The 2197 is an add-on accessory for the Park Tool DT-5 and DT-5.2 Disc Brake Mount Facing Set to enable easier and more efficient facing of disc brake mounts on carbon fiber frames. Features a brazed-on diamond grit surface that is over 100 times more durable and effective on carbon fiber than the cutter included with the DT-5.2. The 2197 sits between the cutter of the DT-5.2 and the brake mount, and smoothly and evenly grinds the mounting surface until it is flat and properly perpendicular to the rotor. NOTE: The 2197 is intended for facing carbon fiber only. Aluminum, steel, and titanium disc brake mounts should be faced using the #2171 facing cutter included with the DT-5.2. For carbon frames that feature aluminum inserts (with a carbon/aluminum hybrid mounting surface), use the #2197. When machining carbon fiber, regularly apply water (or a similar solution) to the cutting surface.