Description A grub screw or set screw is generally used to secure an item against another item, without the use of a nut. This is important, because the ability to secure without a nut makes the grub screw very versatile, and means that a grub screw can be used in applications that require a very small and unobtrusive fixing. The threading travels the entire length of the grub screw, ensuring a firm and effective grip. Specification: Material: Carbon Steel Screw length: 4 mm Grade: 12.9 Color: Black M2.5 x 4mm Packing List: M2.5 Grub Screws x 20 Find other options here: M4, M3, M2.