These Airmar B744V Thru-Hull 50/200A DST TRIDUCER® Multisensors feature depth, speed, and temperature in a single housing–drill only one hole in the boat! The 50/200 kHz, dual-frequency, single ceramic element provides good target detail in shallow water at 200 kHz and good deep-water bottom tracking at 50 kHz. The B744VL’s extended stem-length has the extra height needed for steep-deadrise vessels or thick, cored hulls.