A hex nut is used as a fastener together with a screw or a standoff.

We have here a pack-of-4 nylon hex nuts. The thread size is M2.5, it fits other M2.5 screws/standoffs. The body is in hexagonal shape.

Nylon fasteners have several advantages compared to copper, brass or other metal fasteners. They are lighter, non-conductive and non-corrosive.