I think this is relatively new, at least I never saw it until last night.
One of the Ryobi Plus One batteries plugs into the bottom. It has a high pressure side with a built in gauge and a low pressure - high volume side or air mattresses and the like. It may be just what I need to have on hand to winterize the RV and cabin water supply lines. Rather than keep my pancake compressor up there all the time this may do the job. I'll see what it does this weekend. $60
I have one and the plastic prong n the center that pushes the Shrader valve in broke. I was thinking of putting a new end on it. Other than that it worked well.