A seal for a respiratory mask comprising: an oral sealing portion configured to seal around a user's mouth, and a nasal sealing portion configured to seal on the lower surface of a user's nose and be fully positioned below a bridge of the user's nose, wherein the nasal sealing portion comprises: a first upward extension and a second upward extension , wherein each of the first and the second upward extensions has an internal wall configured to engage with a lateral side of the user's nose, and an external wall configured to provide structure to the nasal sealing portion , the internal and external walls being joined along an upper edge of the seal , and wherein the external walls comprise a pocket having a wall thickness that is less than the surrounding wall thickness, characterised in that the external walls further comprise a thickened rib extending along an upper portion of the external wall, wherein the thickened rib is proximate to but spaced from the upper edge of the seal , wherein the thickened rib has a wall thickness that is greater than the surrounding wall thickness, and wherein the thickened rib extends from a rear end of the external wall towards the front of the seal . an oral sealing portion configured to seal around a user's mouth, and a nasal sealing portion configured to seal on the lower surface of a user's nose and be fully positioned below a bridge of the user's nose, wherein the nasal sealing portion comprises: a first upward extension and a second upward extension , wherein each of the first and the second upward extensions has an internal wall configured to engage with a lateral side of the user's nose, and an external wall configured to provide structure to the nasal sealing portion , the internal and external walls being joined along an upper edge of the seal , and wherein the external walls comprise a pocket having a wall thickness that is less than the surrounding wall thickness, characterised in that the external walls further comprise a thickened rib extending along an upper portion of the external wall, wherein the thickened rib is proximate to but spaced from the upper edge of the seal , wherein the thickened rib has a wall thickness that is greater than the surrounding wall thickness, and wherein the thickened rib extends from a rear end of the external wall towards the front of the seal . a first upward extension and a second upward extension , wherein each of the first and the second upward extensions has an internal wall configured to engage with a lateral side of the user's nose, and an external wall configured to provide structure to the nasal sealing portion , the internal and external walls being joined along an upper edge of the seal , and wherein the external walls comprise a pocket having a wall thickness that is less than the surrounding wall thickness, characterised in that the external walls further comprise a thickened rib extending along an upper portion of the external wall, wherein the thickened rib is proximate to but spaced from the upper edge of the seal , wherein the thickened rib has a wall thickness that is greater than the surrounding wall thickness, and wherein the thickened rib extends from a rear end of the external wall towards the front of the seal . <EOS>