1. Its outside panel is color steel sheet or hot-dip galvanized steel sheet, its strength is high and it will not rusty. 2. Thickness of the door section is 40-50mm, Thickness of steel panel:0.326mm or 0.376mm.3. The structure of door section is steel/polyurethane/steel, its insulation performance is excellent, heat insulation coefficient is high: R=16. 04. 4. Bottom of model U resistant, the encapsulation is good. It adapts to slight uneven ground, and it can stops rain and wind invading.5. All the metal fasteners are made of hot-dip galvanized steel plates, their strength is high, and they do not rust. 6. It has strong torsion spring, the cycle of using is over 100, 000 times.