All Hall Signs aluminum blanks are manufactured at our Bloomington facility per U.S. Bureau of Public Roads Standards. Our standard blanks have 3/8" holes for mounting and radius corners in accordance with the Federal Standard Highway Signs Manual. The aluminum substrate base for our aluminum sign blanks is chemically treated to add longer life and weather resistance. Reflective Aluminum Blanks are covered with material on one or both sides. Choose from three grades of reflective material in seven standard highway colors.