Adding more maps to GPSMAP 64st is easy with our array of detailed topographic, marine and road maps. With 8 GB of onboard memory and a microSD card slot, you can conveniently download one of Garmin's high qualityTopo maps and hit the trail, plug in BlueChart® g2 preloaded cards for a great day on the water or City Navigator NT® map data for turn-by-turn routing on roads (see maps tab for compatibility). GPSMAP 64st also supports BirdsEye™ Select maps that let you load high quality raster maps onto your device and integrate them with your other maps. In addition, the 64st is compatible withGarmin Custom Maps, a map format that allows you to transform paper and electronic maps easily into downloadable maps for your device, for free.