Echonautics BT87M1kW-18 1kW 85-135kHz medium CHIRP 18d Tilted Element Bronze THEchonautics BT87M1KW 85 135kHz 1kW Medium CHIRP 18 Tilted Element Model: BT87M1KW 18 Superior shallow water performance and bottom detail The Echonautics BT87H1kW is a low profile thru hull CHIRP transducer designed to minimize drag and to perform at high speeds. Thanks to the narrow beamwidth, it is excellent for pinpointing fish holding tight to reefs, wrecks, and other structures. Specifications Function Depth and Temperature Frequency CHIRP 85 135