After several attempts I went the duration cooled in winter kitchen as on the nerves that a remedy for the inflowing of the hood cold air had to be mandatory. I have a lot of research, my favorite was a motor outer flap with isolation, but the price of 399, - motivated me to search for effective solutions. Experiments with external plastic registers were unsatisfactory because they did not fit on the existing wall sleeve and test-wise adaptation with tape also were not really close. It flowed still significant cold air to insufficient! Then I came across this Compair-flap and liked spontaneously producing metal. So ordered, for faster delivery was the first evaluation: Very robust metal design of the pipe section, smooth and precise metal doors with high-quality springs, rubber lip seal the flaps! The only tiny gripe: The metal tube has on the side without sealing a relatively sharp cutting edge, because you have something to be careful in handling, but this is not really a problem! Installation proved to be problem-free. I einbaute the flap in the thicker tube piece of the two-part wall sleeve to come as close as possible to the outside wall, I however had to stick another, slightly thicker, sealing tape around the pipe. In thinner tube portion the insulation on the pipe would have been perfectly adequate, which does not justify a devaluation. Then the test: Here a small detail is very strong from: The flaps are not on the bare metal, but on a circumferential rubber lip on. This drastically reduces the rattle when off, and it greatly increases the tightness of the flap. Result: This door was built into the existing wall sleeve (15cm diameter) in 5 minutes without a problem and since then performs absolutely noiseless your service. The effect is dramatic: I have no drafts from the channel of the hood more, the temperature in the kitchen is higher by several degrees and the effect of the exhaust hood seem impaired in any way. They are annoyed about yourself that you do not have much earlier installed this solution, which was as wasted energy :-(. I hope now that the springs even with long-term use of its service do that of course remains to be seen. From today's perspective: A very good product from an excellent supplier at a fair price. Highly Recommended and I can only advise everyone to this solution, since the difference is really substantial.