Park Tool DAG-3An alignment gauge is essential for diagnosing and repairing bent or misaligned derailleur hangers, often the source of shifting problems. The DAG 3 features an all new design, engineered and built to be light, accurate and versatile. The sliding indicator can measure derailleur hanger alignment against bicycle rims of any size, and rotates out of the way to clear seat stays, racks, and other obstacles, allowing 360 degree measurement. The long,