Combination size: Our stainless steel nuts and bolts contained M3X16, M3X20, M3X25, M3X30, M4X16, M4X20, M4X25, M4X30, M5X16, M5X20, M5X25, M5X30, M6X20, M6X25, M6X30, M6X40, each size of 320 pieces, 16 types of models. A purchase can meet your multiple needs. Both the screws and the nuts will be placed in a transparent plastic box with matching labels, easy to use and install. High quality material: screws and nuts hazing for machine made of 304 stainless steel, resistant and durable, it is not easy of oxidar and corrosion resistant, which has high hardness, resistance to oxidation and durability. Inner hexagon bolts are antioxidants, anticorrosion and wear -resistant. It can work well in humid environments. Details of the cross -headed screws: nuts and bolts comply with metric standards, and 304 stainless steel is very resistant and durable. The surface is smooth without burrs. Our threads are very clear and precise, the distance of the thread is approximately 1 mm and the tight threads are not easy to deform and slide during use.