16 gauge mild steel. Powder coated for indoor or outdoor use.Item does not come with mounting hardware.Product Dimensions (inch): 12 - 11.5" x 11.5" 15 - 14.5" x 14.25" 18 - 17.5" x 17.25" 24 - 23.5" x 23.25" 30 - 29.5" x 29.25"
