Each tip is cone-shaped, with a base too large to fit through the small opening in the bag; they are to be inserted through the larger opening before food is spooned in. Tips can be used with pairs of adapter rings: an inner ring is dropped inside the bag and pushed part way out the hole, a tip is slipped over the ring, then an outer ring is slipped over the tip and screwed onto the inner ring. This permits the tip to be changed without emptying the bag.