Outstanding acoustics: The highest in Littman mechanical stethoscopes. Tunable diaphragm: Hear high or low frequency sounds by slightly adjusting pressure on the chest piece. Dual-lumen tubing: Two sound paths in one tube eliminates the rubbing noise of traditional double tubes. Headset is easily adjusted for individual fit and comfort, angled ear tubes align with ear canals. Seven year warranty includes free repair during this period on any manufacturing or material defect(s).