My bike has decent sized leather saddlebags, but they are not lockabe and just carrying around my normal riding stuff fills both bags about half way (two rain suits, tool kit, first aid kit, etc.). I intend using this new bag ($145 including shipping), which should easily hold a full face helmet or two half face helmets on the luggage rack behind the passenger backrest. Its also leather so it should look fine with my current bags, and best of all is rigid and lockable. Even hard cases are not that secure, but do deter a casual thief, so I think this one will work as well so that when off the bike I can secure the GPS, I-pass, etc. and not have to take that stuff with me wherever I go off the bike. I may drill some holes through the bottom of the leather bag and use zip ties to secure it fully to the luggage rack so that a thief could not just lift the entire bag off and walk away. I'll send a photo once I receive it and mount it on the bike.