Part of the protection Maasc offers comes from its high-quality seal, which guarantees perfect fitting on the user's face. To do so we developed a revolutionary airtight seal that fits perfectly well the various face shapes with a unique configuration when folded on your face. We used thousands of anthropometric data from the DINED database to patent our seal. Our LFGB CE food-grade silicone seal is very soft to the touch and easily adapts to your face. However, we come in different shapes and sizes! And that's why we designed three different sizes of seal to adapt to various facial dimensions.