I needed a reliable stethoscope for care of a stroke patient and my daughter, an ICU Nurse, highly recommended the 3M Littmann Classic II S.E. Stethoscope, Black Tube, 28 inch, 2201. After some research I learned the technical reasons why this unit is considered as the "standard" by most medical personnel. Aside from the high quality of components, it faithfully transmits key sound waves to the ears from the patient. While I am not skilled at descerning the differences in verious organ sounds, taking blood pressure is so much easier than with the "cheap" units I previouly used.  It's well worth the price of investment in a quality piece of equipment.