These are Grade 8 (Class10) Zink Plated nuts that were manufactured here in the USA.
These are flange nuts which are more expensive than standard nuts. Flange nuts provide more even clamping pressure than a nut and washer. These specific nuts also feature locking serrations on the bottom of the flange that keeps the nut from backing off or loosening from vibrations.
Send me a message before ordering for a combined shipping price on multiple orders.