We believe this is a tool everyone should have in their toolkit. If you don't know when your chain needs to be changed then you won't know how worn it is. Once the chain becomes worn enough, the drivetrain wears with it, and will no longer be compatible with a new chain. At least the rear freewheel or cassette will have to be replaced at that point, along with the old chain. We think buying this inexpensive tool is a better deal!
Designed to accurately indicate when a chain reaches .5% and .75% which most chain manufactures recommend replacement. Chain wear indicator is a simple go or no go tool.