Provides Bottom Tracking ability to Optimum and Digi-Troll electric downriggers. Network up to four downriggers to troll at set distances from the bottom through this single transducer.Allows Optimums and Digi-Troll downriggers to use the Bottom Track feature to keep your trolling weight a select offset distance from the bottom.Provides full-color sonar data to the master Optimum LCD screen.Length: 28′