16 gauge mild steel. Powder coated for indoor or outdoor use. Current production timeframe is 10-15 days. Item does not come with mounting hardware. Product Dimensions (inch): 12 - 11.5" x 11.5" 15 - 14.5" x 14.5" 18 - 17.5" x 17.5" 24 - 23.5" x 23.5" 30 - 29.5" x 29.5"