These especially small masks were specifically designed for use on small exotics such as pocket pets and birds. The small circuit hooks up the same way as a non-rebreathing circuit does to an anesthesia machine. The masks fit tight around the nose and mouth. Soft conforming cone can be trimmed to custom fit animal’s nose. The oxygen/gas tube position can be adjusted inside mask. Also circuit can be taped to the table to help keep it positioned on the animal’s nose or muzzle.