12-gauge and 14-gauge tubing are two options of square tubing available to you for your structural framework. The 14-gauge tubing is 2 ½ x 2 ½ square tubing and the standard for your framework. The 12-gauge tubing is the 2 ¼ x 2 ¼ square tubing that is available at an additional cost. While this tubing is smaller in size, it is thicker steel which offers you an extended rust-through warranty.