Nut connect bolt or screw fastening screw together to play the role of the part, all production machinery must be an original. Nut variety, we have a common national standard, British standard, American standard, nut on the subject. nut according to different materials, divided into carbon steel, high strength, stainless steel, steel and other major type. According to the different product attributes corresponding to the national standard number is divided into ordinary, non-standard, (old) national standard, the new national standard, American, British, German standard. Different sizes ranging from threaded into different specifications. The general national standard, German standard expressed by M (eg, M8, M16), American, British or # that is used scores of specifications (8 #, 10 #, 1 / 4, 3 / 8) Fasteners