A bottle has a closed bottom, an open top and a peripheral cylindrical side wall. A nipple has a lower section in the shape of a truncated hemisphere, an intermediate section in the shape of a cylindrical, and an upper section in the shape of a hemisphere. The nipple has a hole, an interior surface and an exterior surface. The exterior surface includes a plurality of spaced hemispherically shaped projections including a plurality lower projections on the lower portion, a plurality of upper projections on the upper portion, and a plurality of intermediate projections on the intermediate portion. An adaptor removably couples the nipple to the bottle.