The next generation in electronic stethoscopes stethoscopy combining impressive acoustic amplification, electronic noise filtering and comfortable ergonomic design. The 657 features: Amplifies up to 16x (24db) over traditional acoustic scopes. Patented piezopolymer film contact microphone provides wider frequency response than acoustic mikes used in competing models. Three frequency modes: Bell (15-200Hz) for cardiac sounds, Diaphragm (100-500Hz) for lung sounds, Extended Range (15-4000Hz). 16 level volume control. Holds last mode and volume setting for convenience. Auto-shut off after 3 minutes extends battery life. Battery warning LED signals when replacement needed. Binaurals fixed at 15? angle for snug aural fit. Specially constructed ADSOFT PVC eartips for the ultimate in wearing comfort and acoustic seal. Lightweight and compact weighs under 6 oz., measures just 28. Uses 3V Lithium battery (included). Made in Korea. 2 year warranty.