If you want to test your cards, you will need to use Lexar 400 Professional Card Reader or Lexar SD Card Reader. Normal cards have only a line of gold fingers, and our lexar 1667X SD card has two rows of gold fingers, but the USB 3.0 card reader is tested at speeds shorter than the gold finger, so you should use the Lexar professional 400 card reader or Lexar SD card reader on the 1667X SD card to achieve the maximum speed.
Ordinary card has only a row of gold fingers, our lexar 1667X memory card has two rows of gold fingers,but ordinary USB 2.0 card reader and ordinary USB 3.0 card reader can only test far less than a row of gold fingers' speed,therefore test our 1667X sd card use must Lexar professional SD card reader, in order to achieve maximum speed.