The Park Tool OBW-4 is a specialty bicycle wrench designed for the installation and adjustment of side pull and dual pivot bicycle rim brakes. Its unique offset design and thin profile (2.1mm thick) allow it to access tight places where standard wrenches would be impractical.
The OBW-4 features 10, 11, 12, and 13 mm wrench openings to fit wrench flats found on many side-pull and dual-pivot brake calipers.