Generally speaking, there are two kinds of hex flange nuts: non-serrated flange and serrated flange. These two types have different effects for different applications.

Serrated flange nut mainly in order to increase the friction resistance between the end face,  and to prevent loose, and also easier to dissiplate head.  It is more suitable for vibration, and the enviroment with frequent changes in head and cold.  However,  Serrated flange nut is more easy to damage the workpiece surface. So, it is not suitbale for the parts need prequest disassembly.

Serrated flange bolt and nut do not need use together. For some situation that is not sutibale for serrated flange nut, we also can use nylock lock nuts, all metal lock nuts(metal insert lock nutsand 6 stamping lock nuts).

Titanium serrated flange nut, nylon insert lock nut, all metal lock nuts are widely used in racing with its perfect weight and strength feature compair to aluminium and stainless steel.