Park Tool CC-3.2 Bicycle Chain Checker A worn bicycle chain can cause poor shifting and in time can even cause excessive wear to the derailleur and rear cogs, causing a much more expensive problem. That's why bike component manufacturers recommend chain replacement at regular wear intervals. The Park Tool CC-3.2 is a go/no-go gauge designed to accurately indicate when a chain reaches 0.5% and 0.75% wear (or "stretch"), the points at which most chain manufacturers suggest replacement. The CC-3.2 is long, accurate and features permanent measurement markings. The CC-3.2 works on most derailleur chains* from 5 to 12-speed. For 5-to-10-speed chains, replace chain just as the gauge fits the 0.75% side fits flat into the chain. For 11 and 12-speed chain, replace as the 0.5% side fits. Check with manufacturer for specific replacement instructions. *NOTE: For SRAM AXS 12-speed road chains, use the Park Tool CC-4. Park Tool CC-3.2 Bicycle Chain Checker A worn bicycle chain can cause poor shifting and in time can even cause excessive wear to the derailleur and rear cogs, causing a much more expensive problem. That's why bike component manufacturers recommend chain replacement at regular wear intervals. The Park Tool CC-3.2 is a go/no-go gauge designed to accurately indicate when a chain reaches 0.5% and 0.75% wear (or "stretch"), the points at which most chain manufacturers suggest replacement. The CC-3.2 is long, accurate and features permanent measurement markings. The CC-3.2 works on most derailleur chains* from 5 to 12-speed. For 5-to-10-speed chains, replace chain just as the gauge fits the 0.75% side fits flat into the chain. For 11 and 12-speed chain, replace as the 0.5% side fits. Check with manufacturer for specific replacement instructions. *NOTE: For SRAM AXS 12-speed road chains, use the Park Tool CC-4. How to Read the CC-3.2 TRUSTED SINCE 1963 Since our origins in the back of a bike shop in 1963, it has been Park Tool's sole mission to design and manufacture high-quality tools that empower mechanics and riders of all skill levels to service their bicycles. As with our other 500+ tools, our chain tools are a product of our decades of experience and expertise in the industry, in the shop and on the trail.