EASY OPERATION: Simply place the checker onto a segment of the chain then see whether the chain checker lies completely flat on the chain If so, replace the chain. However, the chain is still good to use if the chain checker sticks upright at the 0.75% end. PRO QUALITY AND COMPACT: This precision laser-cut tool is well built and constructed with pro-quality material, forethought, and care for longevity and is easy to store If you are still looking for a chain checker, this 2-in-1 chain wear indicator tool will satisfy your need and is undoubtedly the right choice for you! WHY YOU SHOULD GO FOR IT: As a consequence of the chain wear, increased wear of expensive rear cogs and chainrings will eventually appear Therefore, routine checking for chain wear can prevent problems with shifting performance, and getting the worn-out parts replaced is more economical than a full change and saves bucks efficiently. Colour:Black+White Material:Iron Package Contents: 10x Bicycle chain wear indicator (black x 5 + white x 5) Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.