d4692348___Photons__Electrons__and_Dirt__Notes
[Description] M3 Nut Dimensions: [Size] 5.5mm (0.217″) across flats, 2.4mm (.095″) thick. [Notes] 
From the nut vendor.
Building an Enclosure using SketchUp and 3D Printing | Photons, Electrons, and Dirt
Notes