Shimano BT-DN320 Di2 Internal Battery derailleur the U-lock can be conveniently

the U-lock can be conveniently and easily transported on your bike without any annoying rattling

Elastic Arch Support

Tune the pedal height with removable traction pads(1 and 2mm supplied) and pins

and most importantly

but they're plenty strong so the durability is not sacrificed

Shimano BT-DN320 Di2 Internal Battery derailleur the U-lock can be convenientlyShimano BT DN320 Di2 Battery InternalFull wireless technology means an all new Battery. The BT DN320 fits snuggly and protected within the new Wireless XTR Rear Derailleur and powers the fast and smooth shifting XTR is known for. Features: Protected Battery Tucked safely inside an enclosed space, the battery wont budge even in rough terrain, while remaining completely removable for charging. Longevity 310 MaH provides for more riding on one charge.