FIG. 1 is a left front perspective view of an ornamental design for gel hat in an open position;
FIG. 2 is a left front perspective view of the gel hat inserted over a person's head;
FIG. 3 is a front elevational view thereof in an open position;
FIG. 4 is a rear elevational view thereof in an open position;
FIG. 5 is a left side view thereof in an open position;
FIG. 6 is a right side view thereof in an open position;
FIG. 7 is a bottom view thereof in an open position;
FIG. 8 is a top view thereof in an open position;
FIG. 9 is a left front perspective view of an ornamental design for gel hat in a closed position;
FIG. 10 is a rear elevational view thereof in a closed position;
FIG. 11 is a front elevational view thereof in a closed position;
FIG. 12 is a bottom view thereof in a closed position;
FIG. 13 is a top view thereof in a closed position;
FIG. 14 is a left side view thereof in a closed position; and,
FIG. 15 is a right side view thereof in a closed position.
The broken lines showing the person in FIG. 2 illustrate environmental matter and form no part of the claimed design. The broken lines shown in FIGS. 7, 8, and 13 depict features of the article that form no part of the claimed design.