Cylindrical head socket head screws, also known as socket head bolts, cup head screws, and socket head screws, have different names but represent the same meaning. The commonly used hexagon socket head cap screws also have grades 4.8, 8.8, 10.9, and 12.9. Also known as hexagonal socket screws, also known as hexagonal socket bolts. Its head is hexagonal and also cylindrical. There are stainless steel and iron according to material. Stainless steel has stainless steel SUS202 socket head cap screws, which are made of ordinary stainless steel material. There are stainless steel SUS304 socket head cap screws and stainless steel SUS316 socket head cap screws. Iron is classified according to the strength grade of hexagon socket head screws, including 4.8 grade hexagon socket head screws, 8.8 grade hexagon socket head screws, 10.9 grade hexagon socket head screws, and 12.9 grade hexagon socket head screws. Grade 8.8-12.9 hexagonal socket head cap screws are called high-strength and high-grade hexagonal socket bolts.