The card slot will "hold" any size card you have. BUT, the c330 is not programmed to use the sd card slot except for additional maps (like the European maps). It will not read as SD card with POI's or anything else you could load on it. (I couldn't figure out why it wouldn't work - and called Garmin who confirmed this.)
It doesn't matter.... it doesn't work
The card slot will "hold" any size card you have. BUT, the c330 is not programmed to use the sd card slot except for additional maps (like the European maps). It will not read as SD card with POI's or anything else you could load on it. (I couldn't figure out why it wouldn't work - and called Garmin who confirmed this.)