Alton | Thermofor Roof Vent Opener Piston Replacement Partyhouse Crystal-clear 4 mm high-impact acrylic

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Alton | Thermofor Roof Vent Opener Piston Replacement Partyhouse Crystal-clear 4 mm high-impact acrylicThe Thermofor Long Piston Replacement is a direct replacement cylinder designed for Thermofor automatic roof vent openers used in Alton greenhouses. If your current opener is no longer responding properly to temperature changes, replacing the piston is a simple way to restore reliable, automatic ventilation. This heat sensitive cylinder contains a wax core that expands as temperatures rise and contracts as they cool, driving the vent to open and close