Features: 1) Standard: GB, ISO, DIN, ANSI, BS, JIS 2) Material: carbon steel, stainless steel, brass 3) Finished: zinc plated, yellow zinc plated,black oxide, anti. bronze, brass plated, nickle plated and other finishes 4) Size: M3mm - M52mm 5) Grade: 4.8, 8.8, 10.9, 12.9