It incorporates a gas-charged cylinder of adjustable volume. As the temperature rises, the gas expands; it will open a 15 lb window, more than adequate in cold frames and greenhouses. A simple adjustment lets you control the operating range. As temperatures fluctuate, the 12-1/2" long unit will open and close a window as necessary to prevent disasters.
Made in England.
Non-rusting anodized aluminum and powder-coated steel.