a central body, the central body comprising an inlet aperture for receiving a delivered amount of gas, the central body having a rear rim;

a gas inlet rotatably disposed around the inlet aperture of the central body, the gas inlet comprising a central axis and a tube portion, wherein the tube portion receives the delivered amount of gas and has a tube axis, and wherein a tube angle is formed between the tube axis and the central axis of the gas inlet and

the tube angle is between about 0 degrees and about 130 degrees; and

a face cushion attached to the central body and having a front rim; and

a brace supported within the central body, being shaped to conform to the contour of the central body's rear rim, leaving sufficient space between the brace and the rear rim that the front rim of the face cushion fits snugly and substantially air-tightly into the space, the brace thus acting to secure the cushion to the central body.