Park Tool CC-2 Chain Checker

The Park Tool CC-2 gives a quick, accurate reading of chain wear ("stretch") on nearly any bicycle chain, helping you catch a worn chain before it damages your cassette and chainrings. Simply insert the tool's pins into two chain links, press the swing-arm gauge, and read the result in the viewing window.

It's compatible with most single-speed and derailleur chains, including Shimano XTR 12-speed. As a general guide, most 5- to 10-speed chains should be replaced at or before 0.75% wear, while 11- to 12-speed chains should be replaced at or before 0.5%.