A worn chain shifts poorly and wears sprockets at an accelerated rate The CC-3.2 is a Go / No-Go gauge designed to accurately indicate when a chain reaches 0.5% and 0.75% 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 Longer design measures a greater length of chain, giving greater accuracy 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 10-speed compatible Made in the USA and covered by Park Tool's legendary limited lifetime warranty