DID 520ZVM-X S&S -120 ZB Super Street X-Ring Drive Chain - SilverDID 520ZVM X S&S 120 ZB Super Street X Ring Drive Chain Superbike Strength D. I. Ds ZVM X Series has greater strength than the VX Series and is designed for heavyweight motorcycles with Tremendous Torque and Horsepower. Longest Wear Life The twisting action of the X Ring increases its sealing performance and its four contact points minimize power loss. Quicker Response The ZVM X Series' Direct Energy Transfer, born from our experience in MotoGP, means