Both g2 and g2 Vision comes on microSD or SD cards. g2 Vision has extra features like aerial/satellite photos and stuff.2. "Bluechart g2" - Improved chip for 2106 GPS onwards (some older machines may require software update to use). Garmin specific not standard shape chip.
3. "Bluechart g2 Vision" - SD card chip for newer machines 4x 5x series GPS's.
1 and 2 will not work in the latest machines (they won't fit) and visa-versa.