Double Spring Heavy Duty Automatic Greenhouse Window Opener. Opens Roof Vents An
Automatically opens and close your greenhouse window as the temperature changes. Heavy duty double spring mechanism designed for use in exposed locations. It is recommended for use on both aluminium and timber roof and top hung side vents, particuarly light polycarbonate glazed, in exposed areas to reduce wind snatch effect and provide increased resistance to wind flutter. Finished in a durable polyester powder coating and corrosion resistant throughout. It will lift up to 13lbs.