The X-Tools chain wear indicator will determine if your chain needs to be replaced. Over a period of time every chain will stretch resulting in poor shifting and the high possibility of the chain snapping. The industry standard for chain replacement is when the chain wear is between 0.75% and 1.0%. Simply place one end into a link on your chain and if the 0.75% side fits in your chain will soon need replacing, if the 1.0% side fits in replace your chain immediately.
Buy X-Tools Chain Wear Indicator Tools from Chain Reaction Cycles, the World’s Largest Online Bike Store.