130 mm x 80 mm with eight 12 mm holes to accommodate 8 large screwdrivers. Back plate is 50 mm.

Screw drivers pictured are from Halfords.

3 x 3 mm mounting holes on the back plate. You may want to add more layers to the shell if drilling the holes for bigger screws.

******** new added version 2****** Ver 2 has 3 x 4 mm mounting holes for better screws and I have increased the the screwdriver recesses to 14mm to allow the drivers to be more secure and drop in further.

Also mount other way up for more strength. Unlike my pic :)