I'm kind of looking for something for my Ram. I have a Weathertech tool box, but no auxiliary fuel tank. At the present time I'm using 2 5-gallon plastic fuel cans in the tool box. I don't carry much in the way of tools, so I've got lots of room. My old truck had a 35 gallon OEM tank, and a 35 gallon auxiliary tank. The new truck has a 32 gallon OEM tank, which is a bit small. I hate truck stops, so I prefer to fuel up without the 5th wheel attached. We rarely travel over 300 miles in a day any more so the OEM with the extra cans works...but barely. I'd like to have a bit more cushion, and an easier refuel than the fuel cans.