Allen Hex Drive Size: 4 mm Metric; Package Includes: 50 PCS M5-0.8 x 20mm; | Diameter of the head: 8.72mm (max), Height of the head: 5.0mm (max); Screw Length: 20mm (excluding the height of the head) | Specifications described in the pictures. Contact us if you have any questions. | Thread: Full Coverage; Thread Pitch: 0.8mm; Color: Black | Made of grade 12.9 alloy steel, which provides good strength and corrosion resistance in bad environments, ideal use in indoor and outdoor projects.