What is an alfine mu-s705b di2 8-speed motor unit? Is it a motor? I've searched the net and found plenty of them for sale, but not one description, explanation, picture assembled on bike. I like the concept of the internally geared rear hub for mid drive(chain wheel drive) bikes. No front or rear derailleur and option to use of a heavy BMX chain or even Gates Carbon Belt drive. I like running my motor through the gears.