DiamondPlate aluminum fire door signs pack a host of advantages to ensure your investment pays off.  - These anodized aluminum plates are made of 20 mil thick aluminum and 3 mil thick 3M 467MP high-performance acrylic adhesive that permanently fuses the sign to the door.  - The legend is sealed into aluminum and cannot be abraded.  - Signs withstand traffic, constant abuse, salt spray, chemicals, and temperatures up to 1000°F.  - Matte finish ensures your message is not hidden by glare. - DiamondPlate fire door signs promise an outdoor life of at least 10 years and many more indoors.