The ornamental design for a frame for a fullface respirator mask, as shown and described.
FIG. 1 is a perspective view showing the new design for a frame for a full face respirator mask;
FIG. 2 is a front view thereof;
FIG. 3 is a left side view thereof;
FIG. 4 is a back side view thereof;
FIG. 5 is a bottom view thereof; and,
FIG. 6 is a top view thereof.
The broken lines form no part of the claimed design, and the shading is provided only to illustrate contour, it is not to indicate any particular texture.