Exquisite Material: These machine screws bolt and nuts are made of high-quality carbon steel, with high strength and hardness, corrosion and rust resistance, smooth surface without burrs, not easy to break or deform, and can maintain good performance in any environment. | Countersunk Head/Flat Head Phillips Design: The machine screws assortment kit adopts flat cross head design, the thread is clear and clean, and it will not slip during use. Hex nuts provide a more precise fit, reduce stress and protect parts and screws. | Easy to Store: These countersink screws bolts and nuts are stored in a storage box, and flat head machine screws and nuts of different sizes are stored separately, so that you can quickly find the size you need, and it is easy to store, transport, and use. | Multi-scenario Application: Suitable for home furnishing, office equipment industry, electronics industry, communication industry, machinery, maintenance, aircraft, ship, bicycle, motorcycle, automobile, chemical industry and other fields. | Package Includes: You will receive 275 pcs in total, 25 pcs for each size: m4x6mm, m4x10mm, m4x12mm, m4x16mm, m4x18mm, m4x20mm, and 125 pcs m4 nuts, the quantity is sufficient and the size is rich to meet the needs of daily use.