Puck transducers mount to the inside of most fiberglass hulls and transmit the sonar signal through the hull. The hull must be of single layer fiberglass construction. (Cored fiberglass, metal or wood are not acceptable) and be free of trapped air and voids. The transducer is glued in with slow cure epoxy.15ft cable and epoxy included. This model will work with 917c, 931c DF, 937c DF, 937 DF2, 957c.