I have used 16 GB cards int he past but don't recommend it. One has a tendency to accumulate large numbers of gcode files on large capacity cards. When you try to open the directory to select a file to print that causes two problems. First, if there are a lot of files on the card it can take a long time to read all of them. Second, for some reason, the file you want to print (the newest one on the card) almost always ends up at the bottom of the list, requiring a lot of scrolling to get to it.
I like to use 256 or 512 MB cards. They load fast and don't hold many files so you don't have to do too much scrolling to get to the one you want.
Ultra MegaMax Dominator 3D printer: [
drmrehorst.blogspot.com]