Park Tool Disc Brake Mount Facing Tool
The DT-4 faces Post Mount disc brake mounts. It was discontinued in 2013 and replaced by the DT-4.2, discontinued in 2015. The DT-5.2 faces Post Mount as well as IS Mount and Flat Mount brake mounts.
The DT-4 can be upgraded for compatibility with newer Maxle and QR-style thru axles by purchasing the DT-UK Upgrade Kit.