This is a demonstration store. You can purchase products like this from Pure Fix Cycles

Chains “stretch” over time, and a worn chain will increase wear on your chainring and cog. Nip that bother in the bud, with the Park Tool Chain Wear Indicator that features a super easy to use “go/no-go” indication of whether or not your chain has hit the manufacturer’s recommended replacement point. Just place it on your chain and you can immediately tell if it’s time to get swappy!