High quality carbon steel. Solid and durable. The M6 network rack screws feature a Philips truss-head with self-guiding pilot points. Screws size: M6 * 16 mm, equals M6 * 0.65 inch; pre-installed nylon washers to prevent scratching equipment; cage nuts are designed for square holes on racks & cabinets usage. 50 sets in each plastic can. Zinc chromate plating to prevent rusting, with firm finishing. Broadly used for standard 19 equipment mounting on cabinets & racks like servers, routers, rack shelves, blank panels, NAS & amplifiers.