All Stryker t-tops are made of premium 6061-T6 high tensile aircraft aluminum. Our new premium t-top model the SG900 features a large 2.5" outer diameter tubing for the pre-fabricated upright leg sections and 2" outer diameter on the overhead "hoop" frame for the canvas. The SG600 and SG300 both use 2" outer diameter all around. Shopping guide: many of our customers are surprised to learn that some of our competitors use smaller diameter tubing (1.5" or 1.9") and some use 6063 aluminum which is weaker and has less tensile strength. Stryker also uses solid billet aluminum for the joints, standoffs, and clamps.