Lumiscope"s professional dual-frequency stethoscope is a great product for both home and medical use. It has a zinc alloy single-sided chest piece with dual-frequency diaphragm. A specially designed membrane lock within the chest piece alters the diaphragm to achieve dual-frequency. Just hold the chest piece to achieve low frequency response. Apply firm pressure to achieve high-frequency diaphragm response. Made with a comfortable non-chill ring, lightweight steel binaurals with internal spring, 22" latex-free Y-tubing and deluxe eartips. Comes with a Lifetime Warranty.