You can now buy a 512 mb Garmin memory card for use with a 276C. Howevere, the card won't work straight out of the box unless you've had the unit software upgraded to version 3.70. You can do this by logging on to the Garmin site and downloading the free "WebUpDater" programme. You install this on your PC and then run it with the 276C switched on and connected via the USB port. Once the 276C's internal software is updated the 512 mb card works fine.