This is a replacement cylinder for automatic window opener. High sensitive, automatic respond to weather changes, so you don't need to stay near the greenhouse. Non electric, uses solar energy, open or close the greenhouse vents as temperature rises or . Greenhouse window automatic roof vent opener is great for most greenhouse to open or close window automatically. Time and labor saving, also can supply a better temperature condition of plant's growth. Specifications: Condition: 100 percent New Temperature Range: 20-25 / 68-77 Size: . 33 x 1.5cm / 12.99 x 0.59in Color: black and silver Material: stainless steel and plastic Package Contents: 2 x Window Opener Only the above package content, other products are not included. Note: Light 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.