Park Tool CC-2 Chain Wear Indicator. With the Park Tool CC-2 Chain Checker you can quickly and accurately determine the wear (or “stretch”) of nearly any bike chain. Simply insert the Chain Checkers pins into two links lightly press the swing arm gauge and then check the gauge window for an accurate reading. The CC-2 is compatible with most single-speed and derailleur chains including Shimano XTR 12-speed chains.