I am quite familiar with all the fasteners made of many kinds of metals. There are hundreds of thousands of manufacturers of metal fasteners in China and the fabrication cost is rather lower than it is in developed regions.
Standards: GB, ISO, DIN, ASME, ANSI, or customized;
Type: bolt, screw, nut, washer;
Material: carbon steel, stainless steel, titanium, aluminum, copper, brass, copper nickel, tungsten, molybdenum etc.
MFG: cold forming, hot forging, CNC machining
Threading: CNC cutting, tapping, rolling
Finish: zinc plating (galvanizing), hot-dip coating, anodizing, PVD coating