Sun-U Polycarbonate Rolling door: The hidden designed operator with spring assisted mechanism offers precise balance makes opening and closing your door effortless but high speed. In addition to has a nylon felt running strip for smooth operation with minimal noise and friction.   The Stainless Steel Roller Shutter, perhaps more than any other door has a diverse range of applications. The Stainless Steel has very good corrosion and oxidation resistance which makes them long lasting and reliable.   Helically wound torsion springs are contained within the barrel to counterbalance the weight of the curtain that make it roll-up faster.   Specification: 1.         Quick and Quiet DC motor with a design of tiny seam, non-metallic materials for fast and slient functions. 2.         Beautiful and Durable Professional anti-rust technology, which makes the roller door beautiful, durable and anti-add and base. 3.         Automatic Safaty System Safety and anti-pressure. The door bounces upward immediately when encountering resistance in lowering; and stop immediately when encountering resistance in rising. 4.         No Worry about Power Outages Able to switch to manual mode and open the door easily when encountering power failure. 5.         Simple Fine-Tuning Patent quick locating system. Easy maintenance, no use of maintenance tools. 6.         Easy Maintenance Spring torque regulator can fine-tune the spring torque when the spring is loose because of long time using. 7.         Additional Functions Can be used for the central control system with sensor eye, UPS, smoke sensor, alarms, and other equipments to form a perfect security environment.