The ornamental design for a stabilityplatformball, as shown and described.
FIG. 1 is a perspective view of a stability platform ball, showing our new design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a bottom plan view thereof;
FIG. 4 is a side elevation view thereof; and,
FIG. 5 is a perspective view of the stability platform ball depicted in FIGS. 1-4, illustrating the attachment of the stability platform ball to a board.
Although only a single side elevation view is shown, it will be appreciated that other side views are identical to that which is illustrated. The broken line showing of portions of the stability platform ball depicts environment and forms no part of the claim. Additionally, the broken horizontal lines between the shaded and unshaded surfaces form the boundaries of the claim and form no part of the claim.