Just as an addition to that helpful and correct info:

Generally speaking in spite of what Garmin say, you can probably use any size of SD/microSD card in a nuvi. That includes cards over 32GB [exFAT format] which have been reformatted to FAT32 using third party software [you can't do that with Windows]. Garmin says maximum for 7x5 is 16GB and that's simply not correct. My 765 happily reads a 64GB in FAT32. The problems with large cards arise because they can be loaded with lots of map data so it is then easy to exceed the maximum map family and map tile limits of the unit. Outdoor units do have a much higher tile limit compared to nuvis but you can still exceed them using very large cards. In general, there's not much point going above 16GB for use with nuvis imo.

At the base of Post #1 it shows Garmin's official table with member's corrections in red. The corrections show the maximum size confirmed to work in various units, not the absolute largest card which the unit is capable to read from and write to.