DID 520ERV3 Series gold X'ring race chain is used by most factory race teams because of it's superior strength, low friction and great looks. D.I.D X-Ring reduces friction by twisting between the side plates instead of being squashed. Normal O-Rings and other makers' modified O-Rings have squashed points that increase friction. The twisting resilience of the X-Ring's four sections greatly increases its sealing performance. This keeps the dirt out and the lubrication in much better than any other O-Ring. X-Rings have the greatest wear resistance of any other type of O-Ring or Non-O-Ring chain.