p style="margin: 0px; text-align: justify;">Some Littman tubing is single lumen, or only having one opening and the high-end models are double lumen. The reason for double lumen design is the advantage in the sound quality when two separate tubes are used for listening to body sounds. An additional advantage to the Littmann stethoscope two-tubes-in-one design is that noise artifact created by separate tubes rubbing together is eliminated. The tubing in Littmann stethoscopes have never contained natural rubber latex or dry natural rubber as components, with the exception of an extension used on the Anesthescope and the Ploss monitor.</p