To improve chain movement and uneven wear on drive parts, most manufacturers recommend replacing the chain at or before the point where 0.6% chain stretch occurs. Now you can quickly and accurately determine the wear and stretch value of any chain. Simply insert the pins of the chain check tool into the two links of the chain, push on the gauge arm, and then read the exact value from the gauge window. To reduce the effects of poor movement and uneven wear on the drive, most manufacturers recommend replacing the chain.