D.I.D.'s 520ERV3 chain is a premium X-ring chain with the superior strength and low friction drag required for today's high horsepower motorcycles. The X-ring's four contact points greatly increase it's sealing performance. This keeps dirt, dust and mud out and retains lubrication much better than a O-ring chain. X-rings have the greatest wear resistance of any other O-ring or non O-ring chain. D.I.D.'s X-ring construction reduces friction by twisting between the chain side plates instead of being squashed like normal O-rings.