I have a 24K MidAtlantic topo micro SD card (4gig) that works fine in my GPSMAP64S But is not recognized by BaseCamp software, I don’t know why and Garmin C/S could not help either. I have now purchased the Garmin 24Ksoutheast topo. No longer need the mid Atlantic card. If you don’t care about using it with BaseCamp or you can figure it out, you have a deal at $ 25.00. I did not see a classified thread, hope this is ok post.