The topbox is a 40, though I wonder if there was a taller one, mine won't accept a helmet which would be nice. The side cases are 35s. I took them w/o the topbox on this trip just to see what living on 70 liters for a few days was like. Other than adding a tent, sleeping bag, and pad - I could pretty easily travel for months with them, so the topbox will make things more cushy. The right side of my cheapo Givi rack sticks out a bit... I measured the distance from the outside edge of both side cases and came up with 38", so I don't really care that they're off center, which was unnoticeable when riding. I even put more of the weight in each one trying to throw off the balance, but again I didn't notice bupkis. The rack is Givi PLR6401 and my sole reason for buying it was cost: $113.84, a little more than half what I'm seeing them for now. I bought from http://www.cli-maxridinggear.com/servlet/StoreFront though they're $190 now, most stores have them @ $200+ For the most part the Tiger/Givi/Caribou combo works ok. Caribou built their cases to work with the rack, not knowing what bike the rack would be installed on. So the lock on the left side box really has to be worked to get it on or off, especially with the topbox on. This is due to the top side of the lock hitting the grab rail as you turn it. But I can live with this.