I have the orchid wax model. With the setting knob all the way in, it doesn't begin to open until the internal temp in the greenhouse reaches 85 degrees. Other than that it performs as advertised.

Madam's Woman cave also known as he Orchid greenhouse needs these as the outside temperature range from 40 degrees F to 100 degrees F on the same day. They work perfectly opening and closing the vents as needed.

I placed this unit in my greenhouse on a side window to create better cross ventilation. I already have two of the same vent openers that operate the ridge vents on the greenhouse and they have been working flawlessly for the last years. I will admit to trying to save a buck and previously installing a "lesser brand" of opener on the side window. It did not make it a year before failing.

I went back to the tried and true and am happy I did so.

I very much recommend this vent opener.

Works very well in my homemade greenhouse. The closing springs are very strong.