Industrial use LARGE Custom NFPA Diamond Labels - Aluminum. 1ft to 4ft wide Adhesive Backed for Outdoor Use. These Huge NFPA Diamond Labels are tough enough to last even in harsh environments. Simply pick the Number you want in each of the top 3 boxes and Symbol you need for the bottom box. The National Fire Protection Agency (NFPA), in section 704 of the National Fire Code, specifies a system for identifying hazards associated with various materials. Proper identification of such hazards is essential for anyone who needs to handle such materials, and emergency responders. Contact us for help in determining what #'s you may need. Numbers are additional in cost.