The Park Tool DAG2.2 Derailleur Hanger Alignment Gauge can help solve a multitude of derailleur shifting problems, most notably with index shifting systems. Updated over the longstanding DAG-1, the DAG-2.2 utilises a longer measuring pointer, longer threaded stud and a longer, narrower alignment boss to fit a wider variety of bikes. This tool is extremely steady in operation and is simple to use. 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. The DAG-2.2 is made of heavy-gauge steel and is chrome plated for long shop life.