An essential for the home workshop of any high mileage rider, chain checkers save you money on cassette cogs by indicating chain stretch.
Rear cassette cogs, which can get expensive, will typically last 2 to 3 times as long if you change the chain whenever it reaches a certain amount of stretch.
The Park CC-2 is the easiest to use and the more accurate of type of wear indicator and is what we use in our workshop.
Compatible with all bicycle chains. For 7 to 10 speed chains, replace the chain at 0.75% readings. For 11 and 12 speed chains, replace at the 0.5% reading.