Bosch Professional 18V double battery wall mount

Arguably slightly easier to hit the release button and takes up a little less wall space.  Requires four 4x50mm screws - assuming a 30mm depth wall plug.  May be fine with just two, depends what you're attaching it to.

Back-to-back and projecting from the wall.  Added a slight chamfer to the tips of the holder as at least the 12Ah version is slightly wider there after the additional contacts that were added in the slot.