Nut with round head, generally used to match bolt, material can be made of stainless steel/carbon steel/brass/aluminum /PP nylon bar, automatic lathe turning.
In order to prevent the oxidation and rust prevention of the surface of carbon steel and aluminum and copper, the general surface treatment is passivation/oxidation/zinc plating/nickel plating/dak rust and other processes.
Can come to the drawing or provide samples to be customized.