These two new Dual-Frequency Stethoscopes by Labtron feature a single-sided chest piece with dual-frequency diaphragm. Skin contact only provides low frequency response, much like a dual-sided bell chest piece, while firm pressure enables high frequency diaphragm response. Other features include a comfortable and non-chill ring, lightweight binaurals with internal spring and deluxe ear tips. The Professional Dual-Frequency Stethoscope (430) features 22-inch latex-free Y-tubing, while the Cardiology Dual-Frequency Stethoscope (435) features 19-inch latex-free, extra thick Y-tubing for outside noise reduction. Both come with a lifetime warranty.