This is a zinc plated steel machine screw assortment with both slotted pan and slotted flat (countersunk) head styles. It also has matching hex nuts, flat washers and lock washers. It comes in a steel 10" x 13" box that is clearly labled and has a removeable plastic tray, hinged lid and latch. It includes the following sizes : M3X6, M3X10, M3X12, M4X6, M4X10, M4X16, M5X12, M5X16, M5X25, M6X12, M6X16 & M6X25. You will find that these sizes are very common in automotive repair, industrial maintenance, hobbies and more. Contains more than 1800 pieces of hardware!!