Not sure, but I think so. these are additions to the city nav maps for the topo features. kinda like an overlay of USGS maps that can be downloaded and run at the same time as the normal city maps
Looks like you need a sd card or else it'll overwrite your preloaded maps. This is per uploading instructions.
Sd card will enable user to switch back and forth between maps . So it seems with garmin nuvi 260. Kinda like buying an sd card map for europe or such.
Buying a blank card this weekend.