Pairing the new Deore -RD-M6250 long-cage derailleur with a standard 10-51t cassette (cassette sold separate) gives all types of riders the range and robustness to tackle every trail on the mountain at a more approachable cost. With built-in Automatic Impact Recovery an impact-deflecting wedge shape steel plate and solid pulley this derailleur stands up to harsh trail impacts while retaining the precise shifting qualities for which Di2 is known. Other features include integrated on-board battery that's protected by the linkage and easily removable for recharging and connectivity with cycling computers and other third-party devices.Di2 technology results in precise and clean wireless shiftingA wide link structure skid-plate design durable aluminum plate and solid pulley add robustness and longevityAutomatic Impact Recovery function instantly returns the derailleur to its original position after impactFeatures Shimano Shadow ES: A slimmer stronger evolution of Shimano's pioneering chain-stabilizing Shadow RD+ conceptTucked safely inside an enclosed space the battery won't budge even in rough terrain while remaining easily removable for chargingThe solid pulley and shielded pulley teeth prevent trail debris from jamming up your flow