Delivery of respiratory therapy

A mask system (1110) for providing a supply of air from a source of air at positive pressure to a patient for treatment of sleep disordered breathing. The mask system comprises an interfacing structure (1180) configured to engage an entrance to the patient's airways, the interfacing structure having a single orifice adapted to deliver the supply of air to at least both of the patient's nostrils. Two inlet conduits detachably connect to the interfacing structure and deliver the supply of air to the interfacing structure. Each inlet conduit is adapted to extend from the crown of the patient's head or from in front of the crown of the patient's head, along a respective side of the patient's face between the patient's eye and ear, and to the interfacing structure. Each inlet conduit has a bottom portion configured to engage the interfacing structure and a top portion in fluid communication with a supply of pressurized air. Each inlet conduit has a wall that extends from the bottom portion to the top portion. Each conduit wall includes at least a portion where, in a cross-sectional view, the conduit wall has a thickness at a first location along a perimeter of the cross-section of the respective conduit that is different than a thickness of the wall at a second location along the cross-sectional perimeter of the conduit.