As the name implies, the "micro SD" is a small version of a SD card, the adapter is a SD size adapter that the micro SD card fits in. It looks just like a SD card but has a small slot for the micro SD card to go in. You may or may not need this, it depends on your computer. Some computers have slots for both and some older ones only have the slot for the SD. The ELite-5 DSI used the micro card, no adapter needed.
Lowrance update their units from time to time for various reasons. When they do this you can go to their site and download the update to your computer, then to the memory card and finally to the depth finder. There are instructions on Lowrances site to check what software version your unit is running, you can also check for up dates while your there. I know there is one update, but your unit may be new enough to have it on it from the factory.
Barnacle Bill
The Elite-5 DSI has no 2d sonar and uses a dedicated DI transducer. So no US2. My personal experience with US2 has not been good, I've tried it on a HB 747C and my HDS-7. On the HB I tried everything but the choke and would've tried it but HB wouldn't send me one. The customer service lady told me it was only for "larger" units. When I bought my HDS I also bought the adapter cable for the US2 but had the same interference as the HB did, so I just mounted the transducer that came with it on the tm. My tm is a Minn Kota Maxxum Pro that was on the boat when I purchased it, I wouldn't spend the extra $$ to get US2 on a new tm. This is just my experience with US2, your results may be better :fish.

