A switch on the cage regulates the spring tension to prevent the chain from jumping. Sudden movements of the chain often lead to significant noise when the chain strikes the chainstay from above or below, or in extreme conditions, even to it jumping off the front chainring. In the ON position, the switch dampens the derailleur cage, thereby reducing chain movement for a quieter and more stable riding experience. With the switch in the OFF position, the derailleur makes it easier to install and remove the rear wheel by relaxing the derailleur spring. The narrow profile of the derailleur significantly reduces damage on narrow and challenging trails. Additionally, the Shadow derailleur has greater vertical stability, preventing it from striking the chainstay. The derailleur is always precisely positioned and operates perfectly. The derailleur pulleys with sealed bearings run quieter and last longer due to their alternating contact with the inner and outer chain links.