John, I believe any pre-formatted SD card of 2 gigs or more should work fine in your machine once you insert it. They're not much money at all. I started PAP therapy in late 2017 and have swapped the original SD card from that machine into its replacement as of February last year. Went from a RESMED AS10 Elite to the AS11 version, inserted the old card, and I'm up and running like before.