Feature: 1. In order to reduce the poor shifting and uneven wear of the drive train, it is recommended to replace the chain before replacing the flywheel; 2. Quickly and accurately determine wear and stretch of any chain; 3. Simply insert the pin of the tool into both chain links, tap the rocker arm gauge, and check the gauge window for an accurate reading, the chain wear indicator will determine if the chain needs to be replaced; 4. Over a period of time, each chain will stretch, resulting in a high probability of poor shifting and chain jamming. It is very necessary to have an inspection tool; 5. For 9-speed and 10-speed chains, replace the chain at or before 0.75% of the reading. For 11 and 12 speed chains, replace at or before 0.5% reading. Specification: Main body material: aluminum alloy Product color: red, black, orange, purple, blue, green Product size: about 135x30x10mm/5.31x1.18x0.39in Product net weight: about 42g Suitable for: Mountain bikes and road bikes