This is a 400 piece, class 10.9 (approximately equivalent to U.S. grade 8) steel, button head socket cap screw assortment with a black oxide finish. The screws are made to ISO 7380. It comes in a steel box that is clearly labeled and has a removeable plastic tray, hinged lid and latch. It includes the following sizes: M4x8, M4x10, M4x12, M4x16, M5x10, M5x12, M5x16, M5x20, M5x25, M5x30, M6x10, M6x12, M6x16, M6x20, M6x25 and M6x30 . These are all very common sizes and are found in many different applications.