A ground-engaging tool system includes an adapter attachable to a work implement and a ground-engaging tip that is releasably connectable to the adapter. To releasably mate the adapter and the tip, the adapter may include a projecting lug post that locks and unlocks with a rotatable, latch-like retainer in the tip. The lug post may be a frustum or frustoconical structure having a truncated flat and an exterior side surface that intersect at a peripheral edge. The shape of the truncated flat, peripheral edge, and exterior side surface may further be delineated by a first radius and a second radius of different dimensions, or by radii having first and second centers that are not coincident in location on the truncated flat.