Window seals are important not only for better energy efficiency but because they also provide better thermal efficiency, soundproofing, humidity and dust prevention and last but not least, also draft protection. M SORA’s windows are equipped with a Q-Ion seal installed in the window sash, whereas the rubber seal is installed into the window frame. That is why all windows have at least two seals; for better soundproofing, however, we recommend an additional third seal.