Unior Professional Chain Wear Indicator Keep Your Chain in Check A worn-out chain can cause problems for your drivetrain. A worn-out chain can cause poor shifting performance and can prematurely wear out the rest of your drivetrain. The best way to check your chain is with a chain wear indicator. The Unior Professional Chain Wear Indicator quickly and accurately determines the wear and stretch of any chain. Simply insert the chain checker's pins into two links, press the swing arm gauge tight, and then check the gauge window for an accurate reading. It is recommended to replace your chain at or before 0. 6% stretch. Features Quickly and accurately determines the wear and stretch of any chain Check the gauge window for an accurate reading High quality materials that will last a long time | Unior | Professional Chain Wear Indicator Black