So far, I have been very pleased with the windows. I got them for casement windows in a sunroom in a house that was built in 1915. The original storm windows are long gone, so for many years, it's just been a single pain window between us and cold Iowa winters. The windows went in reasonably easily and are doing the job of keeping out the cold air exceptionally well. Normally, at this time of year, these windows would frequently get lots of frost and condensation on the inside. So far, we haven't had any frost or condensation, which is a big deal for me. I will admit I was skeptical and nervous about investing so much in something I had never seen in use, but I'm glad I did.