Oasis Value-Sets include genuine Oasis Bell-Bottle Water Bottles and Basic Hold-Guards paired for a perfect fit. Bell-Bottles feature rounded tops to discourage chewing and are color coordinated with the Hold-Guard. The Hold-Guard is sturdy metal with non-toxic powder coating. The guard hangs inside the pet s cage and protects water bottle and cap from chewing biting and gnawing damage. The easy to adjust hanger strap fits many sizes of aquarium-type pet environments (hangs over the upper edge) or wire cages (hanger straps slides through the wird side.) Suitable for fancy mice fancy rats gerbils hamsters sugar gliders and hedgehogs. 4 ounce Bell-Bottle with matching Hold-Guard.