The memory card class 10 is required for Garmin Driving Recorder.
Size: between 4 GB to 32 GB max.
| Class | Minimum performance | Application |
|---|---|---|
 Class 2 |
2 MB/s | SD video recording |
 Class 4 |
4 MB/s | High-definition video (HD) recording including Full HD (from 720p to 1080p/1080i) |
 Class 6 |
6 MB/s | |
 Class 10 |
10 MB/s | Full HD (1080p) video recording and consecutive recording of HD stills (high-speed data bus) |
 UHS Speed Class 1 (U1) |
10 MB/s | Real-time broadcasts and large HD video files (UHS bus) |
 UHS Speed Class 3 (U3) |
30 MB/s | 4K video files (UHS bus) |
Taken from Wikipedia: http://en.wikipedia.org/wiki/Secure_Digital