Humminbird XTH 9 20 P Plastic Thru-Hull Transducer Thru-hull transducer, works with thinner hulls, while internal, steel sleeve provides extra reinforcement Single-, or dual-beam use with 20-, and 60-degree beam angles and operating frequencies of 200 kHz and 83 kHz Not recommended for trailered boats, and professional installation recommended Compatible with many of Humminbird's Piranha, Matrix and numbered series sonar systems Includes fairing block, and is backed by manufacturer's one-year limited warranty