SAT NAV -SD CARD ?

SAT NAV -SD CARD ?

Whats the SD Card for with Sat Nav 

the SD card holds the map information for that area 

If Sat Nav unit is SD card type ,
then it should be noted when inventorying/inspecting into pinnacle and advertising on ebay if the SD cad is missing 

If unit doesn't have SD Card then maps wont show 

What can buyer do if SD Card is missing ? 
These are available aftermarket (can be bought on ebay ) or genuine as replacement units and range is cost from $40 to $400 
Buyer will need to know Sat nav Model details when purchasing SD Card