Park Tool Bicycle Chain Measurement Tool CC-3.2

A worn bicycle chain can lead to poor shifting and, over time, may cause excessive wear to the derailleur and rear cogs, resulting in a much more costly issue. That's why bike component manufacturers recommend replacing your chain at regular wear intervals. The Park Tool CC-3.2 is a go/no-go gauge designed to accurately indicate when a chain reaches 0.5% and 0.75% wear (or "stretch"), the points at which most chain manufacturers suggest replacement. The CC-3.2 is long, precise, and features permanent measurement markings. The CC-3.2 works on most derailleur chains* from 5 to 12-speed.

CC-3.2 Features
5-to-10-speed chains: replace chain at or just before 0.75%
11-to-12-speed chains*: replace at or just before 0.5%
Check with manufacturer for specific replacement instructions
*Use the CC-4.2 for SRAM® Flattop™ and SRAM® T-Type 12-speed chains.