I made this since my Hikvision cameras were bigger than my electrical junction boxes. The base junction box is from Lowes and the brand is Cantex. It has 4 holes in a 3 1/2 in circle. The cameras are a Hikvision clone that have 3 holes on a 4 7/16 circle. I made this as a template to cut out plastic sheet, but could be used as the ring itself. I included the FreeCAD file to edit it.