The MMC cards supplied by NRG Systems for use in the Symphonie Logger are warranted to work with the Symphonie Logger. Confusion can arise when an SD type card is used as well as having the form factor of the MMC match the logger. SD type cards will NOT work in the Symphonie Logger and typically, MMC sizes greater than 64MB will not match the form factor. So, although it is possible that a Radio Shack type MMC will work, to avoid any mistakes and the potential loss of data it is always recommended that NRG Systems 16MB MMCs be used.