FIG. 1 is a front perspective view of an adjustable forehead support dial for a respiratory mask according to our design;

FIG. 2 is a reverse perspective view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a top view thereof with the bottom view thereof being identical thereto; and,

FIG. 6 is a left side view thereof with the right side view thereof being identical thereto.

The broken lines illustrate environmental structure of the adjustable forehead support dial for respiratory mask which forms no part of the claimed design.