National Traffic Signs sign brackets are cast from high strength aluminum alloy 360, under 400 tons pressure, and tensile strength 45,000 PSI and are tumbled and degreased for smoothness and ease of handling. Our wide and extensive range of brackets are used on round, square, u-channel, and wood posts. Mounting hardware comes installed on brackets saving time and hassle of counting loose pieces. All brackets are drilled and tapped to receive 5/16” set screws.