The ornamental design for half hats, as shown and described.
FIG. 1 is a perspective view depicting an embodiment of the half hats, as disclosed herein; and,
FIG. 2 is a top view thereof. The broken lines showing the outer layer ‘X’ of the back adjustment strap are shown for informational purposes only and form no part of the claimed design; and in FIG. 1 and FIG. 2 the broken lines on either side of the seams radiating from the center of the crown represent stitching.