These veterinarian approved glass bottles eliminate evaporation and spills, as well as residual or airborne bacterial contamination. Water is always fresh and clean. Easy to install, fits most cages, and all components can be sterilized. Includes stainless steel hardware, quick-release locking bottle holder, and special nontoxic stopper. Perfect when you plan to do some traveling with your pet bird! Medium tip is 7/16", large tip is 5/8".