I've got the Garmin 441s installed now, looks great, does not take up a lot of room and the screen is large enough to not have to struggle to see. The controls, like zoom in and out, respond quickly and the internal antenna works so well that it even gets signal in my garage (not full stength but it shows what street I'm on). I'm excited to get it into the water and try it out. As updateable maps on the garmin website and has a ton of other functions like sonar, tide charts, fishing info, custom alarms, SD card slot, water temp, 3D map view, tracks other ships location and direction (if you have a dsc radio), and a bunch of other stuff. For about $300 on eBay I got a used unit that was in like new condition and I am extremely happy with the purchase. The screen size is 2.4in x 3.2 in or 4.0 diagonal (10.2 cm). You can do split screen with GPS nav and sonar or full screen for either one. The sonar transducer is the same one I had installed for my fishfinder 160c (although it will work with others as well) so it was bascially plug and plug expect for the power cable which was different but took all of 5 minutes to install. I love the thing and it's a perfect unit to use without dropping a ton of money. It is was better than I expected it to be, could not be happier about the purchase. I will post pics and/or video of it if you like, just let me know if you are interested in seeing them.