Triple Spring solar greenhouse vent openers. Corrosion resistant construction, Balanced lifting action, Illustrated fitting instructions, these greenhouse vent openers have our special Superior Autovent tube with an adjustable opening temperature of 65 – 75°F. Fully open at 20° higher.  Can lift hinged vents up to 30lbs. These triple spring openers work well for wall vents and are also better in high wind situations. Add a wind strap or two for additional wind protection. Free Shipping. If you are interested in purchasing more than 4 of these, we suggest you contact us via phone or email to discuss price and shipping options.