The CC-3.2 is a go/no-go gauge designed to accurately indicate when a chain reaches .5% and .75% `stretch,` the points at which most chain manufacturers suggest replacementFor 9 and 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 fitsLong, accurate and features permanent measurement markingsWorks on most derailleur chains from 5 to 12-speedChain CheckerCC-3.2UPC/EAN/GTIN: 763477001344