Put my new 597 on front. Have been using my intro model that came in my xpress. Too lazy to put 997 permanently in since I rigged it up as a portable. Besides so isn't compatible with US2. That band jut below 21-22 feet must be the thermo line. Fish are above it or in the upper portion. Nothing below it. Most are around 15-18 feet deep. As far as I can tell. I like the 597. Simple to use . Just wish it had 2 card slots. Now I just have my nsvionics card. Would like to have been able to take snapshots.