Park tool derailleur hanger alignment gauge 22the dag 22 is an indispensable shop tool that can be used to both measure and straighten misaligned derailleur hangers solving a high percentage of shifting problems it is made from heavy gauge chrome plated steel and works with 20 to 29 wheels features gauge bar made of heavy gauge chrome plated steel adjusts to fit 20 to 29 wheels replaceable threaded tip upgraded large inner shaft for added strength tighter tolerances for improved acc