Chain Wear Indicator (CWI) by Wippermann
The simplest chain wear indicator on the market. You can see at a glance if the chain is good to go or needs replacement. Very useful to avoid undue cog and chain ring wear.
How to Use
How to Use the CWI (Chain Wear Indicator)
The indicator sits with a gap on a new chain.
Once your chain is so worn that the indicator lays flat, you need to replace your chain or you're going to start to damage to the rest of your drive train.