The X91 features all of the features of the X71 but w/ added depth penetration to 1,000 feet, 3,000 watts peak-to-peak transmit power, all of patented Lowrance fishfinder features include: Grayline, which separates fish and important structure on or near the bottom from the actual bottom; also indicates changes in bottom composition and hardness. Selective on/off Advanced Fish Symbol I.D. which displays fish symbols in different sizes that correspond w/ the size of the return echo. Selective on/off FishTrack which displays the target depth above each fish symbol as a guide for quick and precise lure presentations. Selective on/off FasTrak which displays flasher-style sonar returns, plus the relative signal strength of each target. Advanced Signal Processing(ASP) which continually monitors boat speed, water conditions, water temperature, and other interference sources, then automatically adjusts all crucial settings for the clearest picture possible. The low profile Skimmer transducer w/ temp produces a wider, and a more effective fish detection area and operates at boat speeds up to 70mph! The X91 display is a high definition 5diagonal w/ 240 x 240 pixel high-contrast film super twist LCD that produces excellent resolution, remarkable detail, and target separation even in direct sunlight! For your protection, the X91 has: internal back up memory that preserves sonar settings for up to 10 years, sealed, high impact, waterproof covering for harsh saltwater environments, and a full one year factory warranty. Unit dimensions: 6.9''W x 5.4''H x 3.4''D w/ easy to mount compact case design.