A worn chain shifts poorly and wears sprockets at an accelerated rate. The CC-3 is a Go / No-Go gauge designed to accurately indicate when a chain reaches 0.75% and 1% wear - the point at which most chain manufacturers suggest replacement. The chain should be replaced soon if the 0.75% side fits into the chain before other drive train components also start to wear out fast. If the 1% side fits into the chain the chain is worn out and should be replaced immediately. Made from precision laser cut steel. Consider that if you replace a chain because of wear other vital drive-chain components may need to be renewed too.