The Tolsen 54171 is a self-drilling screw designed for securing metal or aluminum panels, roofs, and facades. These fasteners feature a 3.9 mm diameter and a length of 19 mm, allowing you to skip the pre-drilling step and speed up your installation process. Each screw is finished with a zinc plating for improved corrosion resistance and features a countersunk head with a Phillips drive, ensuring the head sits flush with the surface for a clean look. This pack contains 500 pieces, making it a practical choice for contractors or homeowners working on larger structural projects.