This Autovent opens and closes your greenhouse window for you. Automatic greenhouse vent opener regulates temperature and air circulation for consistent growth conditions Temperature controlled greenhouse opener begins opening at 17°C and fully opens at around 30°C up to 45cm. Powered by the heat of the sun the greenhouse window opener needs no wiring or batteries. Maximum opening approx 45cm depending on adjustment and load. Full instructions provided., Weight: 0.9259415004 Pounds, Manufacturer: Gardening Naturally