Breathing bags in an anesthetic system are collapsible ellipsoid containers that serve as a reservoir for anesthetic gases and as a means for manual ventilation. The reservoir bags, also known as counter lungs, allow visual assessment of the presence and estimation of the volume of ventilation. These bags form a crucial part of most anesthetic systems, since, during normal spontaneous inspiration, anesthetic machines are incapable of providing the needed peak inspiratory gas flow. We have breathing bags in three materials and also in different sizes to choose from.