This opener is the latest in a line of Thermofor vent openers which is suitable for most aluminum and timber greenhouse roof vents. This model is an attractive cost effective unit with a unique opening action, ensuring smooth twist free operation. The cylinder is mounted within the bracket to eliminate projection into the greenhouse. It is finished in a durable polyester powder coating and is corrosion resistant throughout. The temperature at which the unit commences opening is adjustable between 15° and 25°C (59° and 77°F). It will lift up to 7kg (glass area not exceeding 0.75m2 in an aluminium frame) with a maximum opening of 35cm (14").