In the bed under my capper is an eighty gallon aux tank sitting on a rubber bed mat. On one side of the aux tank I have a on board air tank and pump. It is a 3 gallon tank at 200 psi to run the train horn mounted under the box. I also have a 25 foot air hose for tires etc. I carry a boonie box with both top and bottom radiator hoses, a serpentine belt and idler pulley, two fuel filters, spare fuel pump and oil filter. A fold up lawn chair and camp kitchen box that has a propane stove, pots, fry pan, water jug, dishes for 4 and silverware, knives, can opener. Extra retrival gear for the winch. A 6x6 tarp. A large igloo cooler. Chest waders, fly rod and related gear. A 3 step ladder and small tool box. I still have room for my SASS cart and firearms for the weekend shoots. :-laf