Several sizes: M3 * 8/12/16/20, M4 * 8/12/16/20, M5 * 8/12/16/20, a total of 250. In addition, we have a total of 250 nuts in the corresponding sizes. High quality material: Made of 304 stainless steel, with high strength, good resistance to rust and corrosion and long life. Precision design: The screw complies with the standard metric system. The surface of the screw is smooth and no burr, the thread is clear and firm, easy to recesse and difficult to loosen. widely used: The hex bolt is a kind of hex bolt. The main purpose of nuts and bolts is to fix; Are very useful for almost all craftsmen and even the handymen. They are also suitable for various areas such as the construction industry. Storage classified]: All parts are classified and placed in different grids for easy access and storage to avoid confusion and loss. Features: 500 pieces in 4 sizes, diameter of Thread: M3 M4 M5, Length: 8 mm 12 mm 16 mm 20 mm, nut size: M3 M4 M5. Made of 304 stainless steel, it does not rust in a humid environment and is extremely oxygen resistant. The deep and transparent hexagonal screw heads facilitate your work. Our screws and nuts are compliant with the standard metric system. The main field of application of hollow screws is very common in electronics, electrical appliances, chemicals, water, machines and systems, furniture and many other areas. This set is sorted by size / type in a seamless storage box for quick access and protection. Specification: Type of screws: Allen screw Drive type: Six hollow sides Material: Stainless steel 304 Diameter Thread: M3 M4 M5 Size of the socket: M3 M4 M5 Length: 8 mm 12 mm 16 mm 20 mm Package Included: (500 Kit of 500 M4 M5 M4 M5 M5 M5) M3 x 8 mm, 30 pieces. M3 x 12 mm, 30 pieces. M3 x 16 mm, 30 pieces. M3 x 20 mm, 30 pieces. M3 nuts, 120 pieces. M4 x 8 mm, 20 pieces. M4 x 12 mm, 20 pieces. M4 x 16 mm, 20 pieces . M4 x 20 mm, 20 pieces. Nuts M4, 80 pieces. M5 x 8 mm, 15 pieces. > M5 x 12 mm, 15 pieces. M5 x 16 mm, 10 pieces. M5 x 20 mm, 10 pieces. Nuts M5, 50 Parts. Warm tips: The products contain small pieces, keep them out of reach of children to avoid accidental ingestion.