The Humminbird XNT 9 20 T Transom Mount Transducer is a high-speed transducer designed to mount on the transom, or back, of the boat, in contact with the surface of the water, and operate in conjunction with a compatible Humminbird sonar or fish finder system. This unit is a single and DualBeam transducer that features 20- and 60-degree cone angles operating on 200 kiloHertz and 83 kiloHertz frequencies respectively. high-speed transducer single and DualBeam transducer features 20- and 60-degree cone angles operating on 200 kiloHertz and 83 kiloHertz frequencies respectively