A comfortable low-leak mask assembly for use with Non-Invasive Positive Pressure Ventilation (NIPPV) is provided to improve patient compliance and/or treatment. The mask system may include headgear having straps that are substantially inextensible and/or micro-adjustable； and/or a mask and/or cushion that includes various structures to allow enhanced/tailored sealing and/or fit at selected locations on the patient's face.
