@xkoukos

The problem would be that GPSmap 276c doesn't use SD cards. 276c uses the old and very expensive Garmin cards with ridiculous small storage capacity.
BlueChart g2 Large & Extra Large areas would be larger than 512 MB. Some regular areas and possibly all small areas would fit a 512 MB card.
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All depends on the chart you would like to use and what storage size you have on your 276c. If it's [Only registered and activated users can see links. ] you're intrested in then HXEU015R is around 185 MB in file size.