1). All the accessories of garage door are made of hot zinc galvanized steel, high strength, non-rust, impact resistance and durability.
2). Oil-tempered process large torsion spring, operating cycle is more than 50, 000 times.
3). The torsion spring also can be made by Zinc Galvanized Torsion spring.
4). The spring can be customized according to customer's requirements such as Diameter of steel cable, length of each spring, Inner Dia. Of spring, etc.