Flange Nut, M6-1.00, Steel, Class 10, Black Phosphate, 10 PK, Midwest Fastener, Mfr#: 933422

A flange nut has a wide flange at one end that acts as an integrated, non-spinning washer. This serves to distribute the pressure of the nut over the part being secured, reducing the chance of damage to the part and making it less likely to loosen as a result of an uneven fastening surface.