Planters displayed here come in three different sizes, all featuring geometric forms reminiscent of volcanic shards. This resemblance also inspired the name of the collection. The planters are made from Corten steel or aluminum and they are available in a variety of finishes, including a natural rusted look or a powder-coated one.outdoor corten steel decoration adopts new technology to sustainable development and innovation, and is becoming the world's top steel technology. This trim and elegant planter is designed to be used indoors or outdoors as well. Starting out as a soft gray, over time and exposure to the elements, this stylish square planter will evolve to a lovely red-brown swirl.