1. The allowable wear value of the chain shall not exceed 10% of the diameter of the ring chain or the thickness of the accessory;
2. From the plane where the main ring is not bent, the main ring is distorted by more than 10 degrees and should be scrapped;
3. Cracks appearing in any part of the chain, bending or twisting phenomenon and stuck or deadlock between the ring hinges are prohibited and cannot be excluded;
4. The permanent elongation of the chain and single ring shall not exceed 5% of the original length.