HIGH QUALITY: the core technology is the hydraulic cylinder which contains a premium quality plant based wax replacement cylinder for automatic greenhouse window opener or aotovent as they are commonly called. UNIVERSAL : The replacement cylinder is compatible with most greenhouse window openers with single or double springs. SOLAR POWER: This specially designed cylinder, containing this wax, works as a window opening thermostat in greenhouses; there is therefore no need for a power supply. Uses solar energy to heat the cylinder. Open or close the greenhouse vents as the temperature rises or falls, helping to maintain optimal growing conditions in your greenhouse. REPLACEMENT CYLINDER ONLY: A replacement cylinder for greenhouse window opener. The complete set of automatic vent opener is not included. EASY INSTALLATION: Simple DIY installation without obstacles Number of parts delivered: 1 Size: approximately 33.5 cm long