https://www.power-graphics.com/printing-for-outdoor-use/rigid-outdoor-signs/brushed-aluminum-composite.html

These outdoor signs are made of brushed aluminum composite and available in two styles! One has a brushed aluminum finish, while the other is solid white with a polyethylene core and a thickness of 3mm. These stands are 48 x 96 inches and impressively durable; they last 5–25 years indoors and 6 months to 2 years outdoors. Made from eco-friendly materials, they are also scratch- and dent-resistant.