I opted for the monokey box which apparently is designed more for large scooter use, whatever that means. I chose the 30 ltr box which is the baby of the bunch not on cost but it seemed the most suitable. I was concerned the larger 47 litre box would effect rear vision and the 30 ltr box sits perfectly behind me and doesnt interfere at all. Haven't noticed any difference in handling, drag, noise etc so really quite chuffed. Dead easy to remove if not required and top quality fixings, build. Very solid feel, no vibrations. Sounds like I struck lucky though with the fixing points.