1,The bolts and nuts are made of 304 stainless steel of high durability. 2,Generally used on various machine tools and their accessories. 3,Similar to countersunk head screw, the nail head is embedded into the machine, and the connection strength is large. 4,The set included 3 kinds of nuts and 12 kind of bolts to meet your needs. 5,They are integrated in compartment for easy access and storage. Features: The bolts and nuts are made of 304 stainless steel of high durability. Generally used on various machine tools and their accessories. Similar to countersunk head screw, the nail head is embedded into the machine, and the connection strength is large. The set included 3 kinds of nuts and 12 kind of bolts to meet your needs. They are integrated in compartment for easy access and storage. Specification: Material:304 Stainless Steel Size:M3 M4 M5 Crafting Process: Drill the hole according to the diameter of the inner hex to the requirements. Use a cold heading machine to pull out the inner hex. Single one can be used with a hex punch and punched out with a hammer. Package List: 30 Pcs M3x8 Bolt 30 Pcs M3x12 Bolt 30 Pcs M3x16 Bolt 30 Pcs M3x20 Bolt 120 Pcs M3 Nuts 20 Pcs M4x8 Bolt 20 Pcs M4x12 Bolt 20 Pcs M4x16 Bolt 20 Pcs M4x20 Bolt 80 Pcs M4 Nuts 15 Pcs M5x8 Bolt 15 Pcs M5x12 Bolt 10 Pcs M5x16 Bolt 10 Pcs M5x20 Bolt 50 Pcs M5 Nuts