3/8"-16 Zinc Flange Nut

A flange nut is a type of nut that has a wide, protruding rim on one side, essentially acting as a built-in washer, which distributes the clamping force over a larger surface area on the part being secured, reducing the risk of damage and loosening due to uneven surfaces.
Features
Fastens to bolt when joining materials mechanically
Durable steel construction with a zinc coating that provides a corrosion resistant finish
Built-in washer eliminates the need for a separate washer
Driver Type: 9/16 Wrench