BallClapperSkin cutout. Like you see on touring skis. So assuming it's a lighter layup.
Usually skin cutouts are not so recessed, usually a rubber tip with a square cutout in the end that matches the typical width of a tail clip. This one is too rounded IMO to be useful as one of those since the tail clip might just float around a bit. If this is a new mindbender, it doesn't make much sense to me why K2 would put a skin clip on it as it is not a ski designed for touring (they have the wayback), unless the 'c' version of them are filling in the hole left by dispatch, but unsure with that.
Standing firm with my "it looks cool" idea.