a shell and cushion unit including a cushion portion and a shell portion, the cushion portion having two walls and a rear aperture surrounded by a face contacting portion adapted to form a seal with the patient's face, the face contacting portion including a nasal bridge region and side regions extending from the nasal bridge region, the shell portion including a centrally located front aperture opposite the cushion portion and a projection located adjacent the front aperture and oriented towards an interior of a breathing chamber, the shell and cushion unit being a single integral component defining the breathing chamber;

a rigid, generally triangularly-shaped frame with rounded lower corners, the frame engaging the shell portion of the shell and cushion unit, the frame having at least one opening leaving at least a portion of the shell portion uncovered, and the frame being secured to and positively located relative to the shell and cushion unit;

a rigid ring-shaped member with an annular flange, at least a portion of which is adjacent to the front aperture of the shell and cushion unit;

a rotatable elbow having a first end and a second end, the first end engaging with and being rotatable relative to the rigid ring-shaped member and engaging with and being rotatable relative to the shell and cushion unit, a portion of the first end extending through and beyond the ring-shaped member and engaging the shell portion projection;

a swivel attached to the second end of the rotatable elbow and adapted to engage an air delivery conduit;

headgear to support the shell and cushion unit on the user's face; and

anchor points for the headgear formed on the frame, the anchor points including a first anchor point provided on a first side portion of the frame, and a second anchor point provided on a second side portion of the frame so that the centrally located front aperture on the shell portion is positioned between the first and second anchor points.