Kaytee Flat Bac Water Bottle Made of durable clear plastic with a floating duck inserted as a friendly refill reminder Stainless steel spring-loaded dripless sipper Snap-lock Bottle Bracket with the convenient E-Z twist attachment knob allow for effortless bottle romoval and refilling Easily adapts for use either inside or on the outside of the cage Small 4 oz. size is ideal for the tiniest critters like mice, dwarf hamsters and small gerbils