X tools chain wear indicator tool 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 075 and 10 simply place one end into a link on your chain and if the 075 side fits in your chain will soon need replacing if the 10 side fits in replace your chain immediate