I recently bought a pack from there for my UMG that i dont have anymore less than a week ago.
It was a double stick 9.6v 2000mah.
Anything other than a stick you're going to have to open up the UMG and use a dremel to take out a tab in the battery compartment.
If you look down your battery compartment right now, on the bottom left hand side you'll see a plastic rail, thats what has to be removed.
Its still going to be a tight fit even tho its removed, so tight that some people even leave their batteries in the gun to charge.
If you need any further details about the battery, send me a pm.