The Biosound 3550 is a mechanical annular phased array transducer. The 3550 is used for cardiac and abdominal imaging. This probe is compatible and can be used with the Biosound 3000, AU3, Caris and Megas ultrasound systems. This transducer is in excellent condition and can be purchased from Providian Medical. Call today for a free quote at 877-661-8224.