An adapter includes a neck with threads arranged to receive a ring that holds a nipple snug on the neck. A plurality of rings of threads is located within an interior of the adapter. Each ring of threads has a different diameter. The interior is tiered so that a first ring of threads closest to an opening at a bottom of the adapter has a widest ring diameter and a second ring of threads farthest from the opening at the bottom of the adapter has a narrowest ring diameter.
