We got these after our two-year-old son figured out how to yank out the built-in window stops on his second-floor bedroom windows and push them all the way open (he had long since figured out how to unlock the windows). We looked at a million different things, but things like window bars were insanely expensive, particularly with the huge windows we have. I figured that for the price, these were worth a try. We've had them in for a couple months now and they are doing the trick. They were a little hard to install on vinyl windows, and because we have a configuration with two sash windows next to each other with no trim in the middle, we could only install these on one side of each window. But they seem to be working fine, and I worry so much less about our son falling out of the window. Excellent product, especially given the price!