Universal Water Bottle is the versatile waterer that works in every type of small animal home. The Universal Water Bottle includes a free bottle hanger for hanging in any wire cage, as well as an adjustable O-Ring for inserting into the top opening of Super Pet CritterTrail Homes, other modular systems, and Keep-A-Critter Travel Homes. Universal Water Bottle also fits directly into Super Pet's Water Bottle Holder for use in aquariums.