Description: This is an indispensable shop tool that can be used to both measure and straighten misaligned derailleur hangers solving a high percentage of shifting problems. Simple to use: The Derailleur Hanger Alignment Gauge can help solve a multitude of derailleur shifting problems, most notably with index shifting systems. This tool is extremely steady in operation. The tool threads directly into the derailleur hanger. The gauge bar holds a gauge which marks the distance to the wheel. The gauge then is rotated with the wheel to the 3, 6, 9, and 12 o'clock positions, noting any differences in measurements. The alignment of the derailleur hanger is accomplished by applying pressure to the tool's arm. The results can be checked instantly. Gauge bar made of High-strength aluminum alloy, Hardened by heat treatment. Adjusts to fit 20" to 29"+ wheels. Replaceable threaded tip. Upgraded large inner shaft for added strength. Tighter tolerances for improved accuracy. Improved clearance and reach to fit more frame/hanger combos including low clearance thru-axle derailleur hangers. Specification: Material: aluminium alloy Package Size: 27x14x4.5cm/10.63x5.51x1.77inch Package Includes: 1 Piece Derailleur Hanger Alignment Gauge HAG-3