The top section of the tower is made of 1" OD aluminum tubing; in cross-section, the topmost tower section is 10.1 inches on a side (center of tubing to center of tubing).
The middle section of the tower is made of 1" OD aluminum tubing; in cross-section, the middle tower section is 13.1 inches on a side (center of tubing to center of tubing).
The bottom section of the tower is made of 1.25" OD aluminum tubing; in cross-section, the middle tower section is 17 inches on a side (center of tubing to center of tubing).