Premium Carbon Steel : Screws and cage nuts are made of high quality carbon steel and black zinc plating ,making screws extremely abrasion and corrosion resistant. Professional Design: Square cage nut designed for racks and cabinets with square holes, mounting your standard rack equipment into a server rack or cabinet.Pre-installed nylon washers to avoid scratching equipment. Various Applications: The M5 rack screws are widely used for mounting your server rack cabinets, rack shelves, A/V device enclosures, and etc. These M5 cage nuts and screws are universally compatible with all square-hole racks and cabinets. Included Accessories: 50 sets Include 50 screws,50 cage nuts and 50 washers .Pack in a box instead of plastic bag. M5 rack screws, fit most 19" standard racks and cabinets. For rack mounting with square holes.