At home I have you first plugged in the USB card reader and tested the speed.
Unfortunately, the card was writing not go beyond 15 MB / s. I have taken the test multiple times with the same and with other files on both cards. There was no improvement.
Then I got my "old" SanDisk Extreme III 4GB Class 6 20MB comes when copying the same files as in the test previously to over 18 MB / s.
Werd me again soon buy SanDisk