Park Tool CC-3.2 Chain Wear Indicator

A go/no-go bicycle chain wear gauge made by Park Tool, item CC-3.2. It indicates when a chain reaches 0.5% and 0.75% wear and works on most derailleur chains from 5 to 12-speed. Park recommends replacing 5 to 10-speed chains at or just before 0.75% and 11 to 12-speed chains at or just before 0.5%.

Text from OyList