The outer sleeve is not load-bearing and only provides protection, and becomes flattened cooperating with the inner bearing core to provide a safe and loaded grasping force so as to provide abrasion resistance and prolong the service life. The flexible sling is lightweight and only 20% that of the chain with the same load. Thus, even if fell from a high altitude, it will not cause the personal injury. In the same way, the shaking of it on the hook of the crane is not easy to cause damage to the head of lifting workers like traditional lifting tools. In addition, the sling will not produce sparks in explosive or dangerous environments.