Heavy Hex Nut (IS:6623/ANSI B18.2.2/ASTM A-194)
A Flange nut is a nut that has a wide flange at one end that acts as an integrated, non-spinning washer.
Also known as, Nylon insert Flange Lock nut, it is a kind of hex flange nut , with a nylon-filled collar at its back end and an enlarged circular base flaring out from the front end of the nut.