[Double Spring Design] Our solar heat sensitive roof vent opener adopts double spring design, which has stronger thrust force and more solid; You can use two window openers together, it can be applied not only in ordinary areas, but can also in windy mountain area, resist wind twist. [Temperature-Sensitive Ventilation] Our automatic window opener will automatically open and shut your greenhouse window to maintain the best growing temperature and preventing your greenhouse from overheating, efficiently regulating your greenhouse's internal climate. [Premium Material] the solar window opener is built to last and withstand harsh weather conditions. Aluminum frame looks more lustrous, and rust-proof. Colour:Black & Silver Material:Aluminum alloy Package Contents: 2 * Window Opener Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.