Corrosion resistant, solar powered piston extends 12" to open and close greenhouse vents automatically.  Piston extends and contracts adjusting the vent as the temperature changes.  The opening is between 5 - 7 inches and it will open a window pane up to 30 pounds.   Fits most popular greenhouse vents. 

Our "down in the dirt" Customers Say: From Monroe H Spector I ordered the double compartment rotary composter and received and received instuctiond for the single system only (very annoyining)- otherwise great service, good instrucions and a very good unit.... Read more...