Shimano 105 RD-R7100 Rear Derailleur – 12-Speed Direct Mount One Spec Shadow Design 36t Max Low. The Shimano 105 12-speed rear derailleur combines the smooth and stable shifting that is a staple of Shimano Shadow RD design with direct mount compatibility and a wider gear range capacity.Shadow RD offers a low-profile design with single tension construction that prevents the derailleur from hitting the chainstay in rough riding conditionsDirect Mount feature is design for large contempory frames with large section chainstays in particular mountain bikes with thru-axle dropoutsWider gear range capacity and stable shifting performanceCompatible with HG 12-speed chains41t total capacity36t low sprocket maximum34t low sprocket minimum