The requirement and choice for Pro Storage card are as below:

The camera supports UHS-I SD card with video speed class of V30. SanDisk SD (link for purchase from Jingdong Mall: https://item.jd.com/530218.htm...and link for purchase from Amazon:   https://www.amazon.com/dp/B01K... ) is recommended, and the card format should be exFat. Please use card of over 64G storage. There is no upper limit to the storage capacity of the card.

It is also recommended you use SD card with "Extreme PRO" instead of the golden card on the left.

The video speed class is of the latest standard issued by the SD card association, and the speed standard is as shown in the figure:

  1. The camera also supports to use SSD mobile hard drive of USB 3.0 or higher speed. The file format is recommended as exFat, and there is no limit to the storage capacity. (link for purchase from Jingdong Mall: https://item.jd.com/4718623.ht...and link for purchase from Amazon: https://www.amazon.com/dp/B01A... ) 
  2. When the mobile hard disk and SD card are used at the same time, the shot content will be preferentially stored into the former by default.
  3. When the user connects a new storage device, the camera will prompt for speed testing upon first video recording. The video recording may proceed smoothly only when the tested speed meet the standard. The user can also access the storage function in the camera setting, and manually test the speed of a storage device.

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How to format SD card or hard drive with camera?

This function needs firmware v200 or higher version. 

Notice: After formatting with Firmware 200 Beta, you must plug in and unplug the storage device for normal use. With Firmware 201 or above, you can directly use the storage device after it is formatted without plugging in and unplugging.