The HOOK-4 combines the benefits of CHIRP Sonar and DownScan Imaging™ technology to give you a clear and complete view of the underwater environment beneath your boat. It features enhanced sonar sensitivity, excellent target separation and superior noise rejection, making it easier to see baitfish and gamefish targets. With a built-in GPS antenna and proven navigation features, revisiting your favorite fishing spot is simple with the HOOK-4, whether you use the base map, optional high definition chart upgrades, or your own Insight Genesis custom maps.