My HJC XL (not XXL as previously misstated) full face fits only on its side. My HJC L open face fits only on its side, but I have to remove my flat face shield first. The quality of the brackets, tank bag, and top box is very good. Impressive, in fact, considering the cost. I use my top box all the time. Easy to open, close, and remove. When I need more room I add the tank bag and/or side bags. I've not noticed any effect on stability or handling with the top box. Of course I don't carry a load of bricks in it either. That's what the side cases are for.