A set screw is a type of screw generally used to secure an object within or against another object without using a nut. The most common examples are securing a pulley or gear to a shaft. Set screws arefully threaded and has no head projecting past the major diameter of the screw thread.These set screwsare driven with a internal-wrenching hex socketdrive. Features: These set screws are made from 304 stainless steel for rust protection, durability and long service life. They are multipurpose hex socket head set screws that you can simple drive with hex keys. There are 12 common sizes and you can concentrate on your project without worrying about not having the correct screws. Get these total 240 pieces screws so you won't be running off to the hardware store for a set screw for quite a while. Well packed and assorted in a resealable transparent box for convenient carry and storage. Specifications: Material: 304 stainless steel Type: Hex Socket Cup point Color: Silver Size and Quantity: M3*3 20pcs M3*4 20pcs M3*5 20pcs M3*6 20pcs M4*4 20pcs M4*5 20pcs M4*6 20pcs M5*5 20pcs M5*8 20pcs M6*6 20pcs M6*10 20pcs M8*8 20pcs Package Includes: 240pcs x Screws 5pcs x Hex Keys(M1.5, M2, M2.5, M3, M4)