A worn chain shifts poorly and wears the 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% "stretch", the points at which most chain manufacturers suggest replacement. For 9- and 10-speed chains, replace the chain as the gauge fits flat into the chain on the 0.75% side. For 11- and 12-speed chains, replace the chain as the 0.5% side fits into the chain. The CC-3.2 is long, accurate and has permanent gauge marks.