This nice 1/4-20 Flat Nut is 1/4 inch thick with a Knurled Edge and Black Anodize.  Rubber on one side.  
 
Also included at no cost is the 5.0mm x .8 Flat Nut of the same specifications.
 
The 1/4-20 Nut is handy under a number of cameras.  The 5.00 mm Nut fits Action Camera Screws.
 
Two Nuts are in this package.