The DriveSense Ranger Duos are compatible with microSD cards of up to 64GB.
We recommend using Class 10 microSD cards for optimal performance and reliability.
Using a lower class microSD card may prevent the camera from recording data. 
You can read more about microSD speed classes here:
About the Kingston Canvas Select microSD cards (for RAA customers) -
The Canvas cards are a line of microSD cards developed by Kingston and is designed for reliability with HD video recording and photos. 
They come with a Class 10 UHS-I rating and speeds of up to 80MB/s read. 
The Canvas Select cards by Kingston are built to be more durable in that they are waterproof, temperature proof, shock and vibration proof, and X-ray proof.
You can learn more about them here: