Garmin GT15M-IH Plastic, In-Hull, Mid-Band CHIRP Transducer - 85-165kHz, 600W, 8-PinGarmin GT15M IH Plastic, In Hull, Mid Band CHIRP Transducer is designed for fiberglass boats, letting you install the transducer inside the hull rather than on the transom. This setup minimizes cavitation and keeps depth readings stable and accurate at high speeds, helping you navigate and fish more confidently on fast moving boats. In hull installation for fiberglass hulls: Installed inside the hull rather than on the transom to minimize cavitation