Bayliss MK7 Triple Spring Auto Vent Opener

Installed on a Sunshine Gardenhouse. Needed to move the roof vent strut up an inch so this could screw into the flat rather than into the 1/4" width. Measure several times and predrill your holes.
You can remove the 2 outer springs to make installation easier as you check the motion. It feels a bit wobbly as you install, but the action is smooth.

I like this autovent very much, it's well built and works well. The one limitation is that I've attached it to a cold frame, need to get into the cold frame to water, and sometimes have to open the top far enough that the piston comes out of the end. A quick release of some sort would be helpful.

Quick delivery, and easy to fit with clear instructions. Does exactly the job I need it to do: it works perfectly and has proved to be very stable in strong winds.

These are the best vent openers we've used. Depending on your greenhouse design, replacement can be easy or a huge pain; plan your bench layout for access to the opener. A power tube might work for ten years or might fail much sooner; ALWAYS have a spare power tube or a spare complete opener on hand. We've replaced two power tubes on our first opener which we've been using for twelve years. Don't attempt to change the power tube without taking the opener off the greenhouse. Ask me how I know that.