*Type: O-ring chains,X-ring chains,Non O-ring chains *Materials:Superior alloy steel 1.The service life of O-Ring or X-Ring Chain is greatly depended on the wearing between the pin-shaft and the sleeve. The "O" ring or “X” ring will greatly reduce the wearing and thus prolongthe service life by 3-5 times. 2.Model:420V,428V, 428VM,520V, 525V, 530V, 530VM, 630V, 630VM,428V-X,428VM-X,520V-X,525V-X, ...