Extensions are used when you want to stack containers on top of each other. When purchasing an extension, keep in mind that your extension size correlates with the container you will have on the base of your setup. The extensions are made of hardened anodized aluminum with B7 all thread for maximum strength. (Note locking pack mounts are not recommended for use with extensions.)
Use this Extension to stack any Fuel Pack on top of the 3 Gallon.
Use the standard Extension if stacking the 3 Gallon on top of a 1,2 or 4 Gallon Fuel Pack.