The Humminbird 959ci HD DI Combo is a very similar fish finder in terms of capabilities, with the 999ci HD SI Combo, only it does not have the Side Imaging options. Other than this, it pretty much shares all the features with the top unit of the 900 series.
For starters, it has the 8-inch diagonal, full color display, with an 800H x 480 (16:9) pixel resolution, and backlight. It has dual card reader and instant access preset button, and the box also includes a cover for this unit.
As the name of the unit suggests, it comes with Down Imaging technology. The DI sonar can run on two frequencies, 455 kHz / 75°, or 800 kHz / 45°, with a depth capability up to 350 ft. It also has Dual Beam Plus sonar, which allows it to be operated on two frequencies (separately or simultaneously), at 200 kHz / 28° and 455 kHz / 16°, with a depth capability up to 600 ft. Its power output is 500 Watts (RMS / 4,000 Watts (PTP). The standard transducer of this unit is a Transom XNT 9 DI T. This unit does not support 360 Imaging.
The navigational capabilities of the 959ci HD DI Combo include precision GPS, chartplotting and trackplotting. The unit comes with the ContourXD built-in cartography package, but it can also support Navionics Platinum+ or Gold/Hotmaps, as well as Lakemaster charts SD cards. Its memory can store up to 2,750 waypoints, 45 routes, and 50 tracks (20,000 points each). This unit also has Ethernet Networking capabilities, and supports iPilotLink, NMEA2000, and Radar2, but these 3 last features are optional.