The ornamental design for multi-grip bench bar, as shown and described.
FIG. 1 is a perspective view of the multi-grip bench bar.
FIG. 2 is a perspective view of the multi-grip bench bar with bar bell weighs carried by the bar shown in dashed lines, which form no part of the invention.
FIG. 3 is a top view of the bench bar.
FIG. 4 is a side view of the bench bar.
FIG. 5 is the opposite side view of the bench bar.
FIG. 6 is an end view of the bench bar.
FIG. 7 is the opposite end view of the bench bar; and,
FIG. 8 is a top view of the bench bar with the environment in which the bench bar is used shown in dashed lines. The objects shown in dashed lines form no part of the present invention.