This is a sleeved mount for the Baseus 100W PD GaN3 Fast Wall Charger Block. The mount is designed to pass the wall plug through the back. The positive stop on the front prevents the charger from pulling out of the mount when disconnecting a USB cable but can be pushed down slightly to remove the block from the sleeve.
 

Screw holes are 3mm with a chamfer to 6mm. The opening to pass the screwdriver bit through is 11.5mm (diameter of the DeWalt extension I used).