The Exaco Automatic Rood Vent Opener is designed to automatically open and close as the temperature changes, Perfect for making sure there is always proper ventilation flowing through your greenhouse, you never have to worry about whether your plants are okay if there"s a sudden shift in the weather, Crafted from aluminum for durability, you"ll love the ease and simplicity of using the automatic roof vent, Frame Material: Aluminum, Adjusts to open/close with temperature changes, Allows for proper ventilation, Crafted from aluminum for durability, Dimensions: 12""L X 3""W x 2""H, SKU: EXTR142