I dunno about Ridata but I've been using a Kingston Elite Pro 4gb card (now $145 at zipzoomfly.com, somewhat more when I bought mine) in my 660 and it works fine. I'm recording in mp3 format so 4gb is almost infinite, and flash prices are falling very fast, so this doesn't seem to be a great time to spend a lot on flash cards. Later this summer I'll either switch the 660 to an R09 (uses SD cards) or maybe buy some 8GB CF cards and start recording WAV.