Medical apparatus for the treatment of obstructive sleep apnea; medical apparatus, namely, non-invasive ventilation apparatus and instruments; medical respiratory masks for use in treating obstructive sleep apnea; breathing masks for use in treating obstructive sleep apnea; facial masks for medical purposes; oral masks for medical purposes; nasal masks for medical purposes; mouthpieces for medical purposes; headgear for medical purposes; seals and connectors for medical respiratory masks; parts and fittings for all the aforementioned goods.