Park Tool CC-4 Chain Checker
The CC-4 is a drop-in style gauge that measures bicycle chain wear. The laser cut CC-4 accurately measures a long section of chain and strategically comes in contact with the chain in three places, quickly and easily taking the guesswork out of knowing when chain replacement is necessary. A worn chain will cause poor shifting as well as accelerate drivetrain wear. The tool works on any Single speed drivetrain or 5 to 12-speed derailleur chain and is designed to accurately indicate when a chain reaches .5% and .75% wear, the points at which most chain manufacturers suggest replacement.