I agree with this since I have a Mega Cab truck. What I use are Craftsman plastic tool boxes, the low profile box that is 22"L X7.5"W X 4"H. These fit will under my seats and can be moved out of the way to lay my seats down. You did not specify what year of truck, but on my 08 there is also inside storage behind the seats that have two doors that open to allow access to these compartments..