The bag in the picture is 120 liters. I know they have a 60 liter as well. For the ATV I usually stack 2 bags together and tie them down. I do the 120 Liter on the bottom and a 80 Liter on the top. It also serves as is a nice back rest ;).
I was doing an oil change on my Ski yesterday and decided to throw my bag on to show it off to the neighbor. I think these pics show off the capacity and ability to strap it down pretty well.
I totally get it – hauling all that gear on an ATV can be a real pain when you're trying to stay organized. You might want to check out the Dry Water Adventure dry bag – it comes in a 120L size, so you can throw all your gear (bow, food, camp supplies) into one bag instead of strapping down a...