Garmin eTrex 10 ...

No, seriously, Garmin Etrex 10 is a remarkable GPS device! Just look: a new high-sensitivity receiver with GLONASS support, low-power, but high-performance processor, efficient sealing rubber - and all these features at a price comparable to noname car devices!
But an epic fail of Garmin Etrex 10 is a few storage capacity. It seems unclear: today, when a flash memory costs even a dime, why the manufacturer have installed only 8MB of internal memory or simply have not provided a slot for SD card?
It is obviously: with greater storage capacity Garmin Etrex 10 would satisfy the requirements of the 99% of users and beat all other "advanced" (and more expensive!) devices. It is no wonder that the manufacturer, widely advertising useless basemap, insolently states that custom maps could not be downloaded in Garmin Etrex 10!

... and Topo Maps

Nevertheless, loading topo map in a vector IMG format to Garmin Etrex 10 is not easy, but very easy! Simply connect your GPS device to your computer in "Mass Storage" USB Mode and just replace the file of the base map gmapbmap.img by a topo map file with the same name.
Only what we shall download? Detailed topo maps of a whole state have a size of tens of megabytes! However, for most users - fishermen, backpackers and geocachers the whole area is not immediately needed. On the download page you will find a set of topo maps and graphical interface for downloading into your device. Maps are good detailed and their elements are optimized for the monochrome display of Garmin Etrex 10. All this maps are free.