3M Littmann Classic ll S.E. Stethoscope. The Littmann Classic ll S.E. Stethoscope dual frequency tunable diaphragm allows the user to listen to both low and high frequency sounds by simply alternating pressure on the chest piece. Firm pressure allows the user to hear high frequency sounds. Ease off to light "skin contact" and the diaphragm lets you hear low frequency sounds. 3 Year Warranty. 28 Inch.