The Park Tool DAG-3 Derailleur Hanger Alignment Gauge is a precision tool designed to diagnose and correct misaligned derailleur hangers, ensuring smooth and accurate shifting. Featuring a redesigned, universal fit, it works with bikes of all sizes, including those with thru-axles. The long measuring arm provides precise adjustments, while the durable, shop-quality construction ensures longevity. Ideal for home mechanics and professional workshops, the DAG-3 is essential for maintaining optimal drivetrain performance