Automatic Greenhouse Vent Opener with Two Springs Solar Powered Auto Window Opener for Hothouse&Cold Frame Greenhouse Acessories-Lifts 15.4 Lbs

I am thrilled with these venting arms. I built 2 cold frames and installed one lift in each. The top (light) is made out of 8mm polycarbonate. So, they are fairly light. Final results were awesome. You cannot do cold frame gardening without these unless you have nothing better to do than monitor outside temperatures and continually adjust your light throughout the day.The brackets were fairly easy to install. They sit inside my cold frames and I was not inclined to stand them on edge without assistance to install. Measure and drilling was a little tricky.It was a cool day here in the mountains when I finished. Outside temperature was about 55. Inside my cold frame was probably 70ish. You can see from the picture that the frames are partially open.