Useful tool for chain wear: The chain wear indicator shows when a certain wear has been reached. You can replace it before it becomes a problem to keep your bike in good condition and safe. Useful tool for measuring chain wear level. Check the chain wear: If the other end does not snap into place, the chain is new, if it is partially pinched, it is worn, if it is completely clamped, it is heavily worn. Chain Hooks2 hooks on the top of the integrated chain that holds the links during assembly. The operation is more convenient, avoiding oily hands and chain jumps, so you can work more efficiently. Measurement of thread diameterDifferent sizes of round holes can measure the thread M3 M4 M5 M6 M8 M10, and the scale can be used to measure its length. Specification: 2 pieces bike chain wear indicator tool. Compatible with all bicycle chains, easy to install and use. Size: 125 mm. Material: stainless steel, easy to use and carry.