The 3M Littmann Master Cardiology Stethoscope is characterized by the best acoustic response in the Littmann mechanical stethoscope line; with a tunable diaphragm, dual-lumen tubing, and a precision, ergonomically designed, stainless steel chestpiece. Features: Outstanding acoustics: The highest in Littmann mechanical stethoscopes. Tunable diaphragm: Hear high or low frequency sounds by slightly adjusting pressure on the chestpiece. Dual-lumen tubing: Two sound paths in one tube eliminates the r