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I have looked at many sites and this is the going price for the 4MB rewritable memory card.
You need only one card as it is rewritable. You download designs from the Internet and store them in a folder on the PC's hard drive. As you want to embroider a design or several designs, you open the software and choose the location of the designs and send them to the card.
As you add more designs to the card, the old ones are deleted from the card, but remain on the hard drive.
Be sure to back up the folder where the designs are stored each time you make changes or add designs as a precaution against loss. If you accidentally delete the folder or if the PC crashes, you will still have your back-up. You can use a usb flash drive or cd - the flash drive stores more files.