Description: Double spring controlled - Resists wind damage when opening and closing. When temperature between 33° to 44°F, the window opener will keep opening, release the manual ventilation arm. Uses solar energy, environmentally friendly. open or close the greenhouse vents as temperature rises or drops, adjust the temperature approx 15°C to 25°C automatically, be clamped to greenhouse bars. The maximum window opening approximately 45cm/18 inch, depending on the adjustment and load. Window roof vent opener Suitable for greenhouse window up to 7kg. Function: This opener will automatically open and close your greenhouse window, as the temperature changes automatically, maintains the best growing temperature and prevents your greenhouse from overheating. Notice: The iron automatic ventilation window opener in the greenhouse cannot be used in an environment with a temperature higher over 50°C . Specification: Material: Iron Size: Length x Width 36x2cm/14.17x0.79 inches Weight: 600g Package Includes: 1Set Automatic Double Springs Greenhouse Window Opener