The Rotopax 3 Gallon Extension can be used to stack Fuel Packs on top of of the 3 Gallon RotopaX, 3.5 FuelpaX, or 4.5 FuelpaX. However, if you’re stacking the 3 Gallopn on top of 1, 2, or 4 Gallon Fuel Pack you need to use the standard extension.
