FEATURES: Lifts up to 30 lbs No power source required Adjustable Opens automatically when interior temperatures get too high This temperature-sensitive vent opener automatically opens and closes with response to changes in its environment. This device uses temperature sensitive wax inside a cylinder to adjust the opening size of your window or vent. It can be used with cold frame lids, greenhouse windows and small skylights to help maintain consistent interior temperatures throughout the day. The Agtec Automatic Vent Opener requires no batteries or electricity, and begins to open a vent when temperatures hit 55—75°F (depending on how it is adjusted). Ideal for use in greenhouses as proper temperature management dramatically improves growing conditions for plants. Screws directly into polycarbonate panels, wood, or metal frames.