Mobile Phone | Memory Card

Long-term Field Test: 27.09.2021 to date

SanDisk Extreme Pro microSDXC 400 GB

New Memory Card for new Fairphone

The Fairphone 3+ I had put into operation with my old SanDisk Ultra microSDXC 200 GB. It was in the BlackBerry P'9982 for almost six years and still works, even though one folder could not be deleted. As a precaution, I looked for a new memory card with at least 400 GB ... On Amazon.de I read many bad reviews for current microSDXC cards of my preferred brand SanDisk, after which I was very frustrated. Then it occurred to me that in addition to false reviews, product counterfeiting can also be the cause of many customers' bad experiences and I decided to buy locally at my favourite electronics store, Saturn Frankfurt. After all, I have been buying almost all my hard drives there for many years ...


26.09.2021: Memory card SanDisk Extreme Pro 400 GB ordered online at Saturn for collection by the customer (85.99 EUR). Will be provided tomorrow.
27.09.2021: Memory card collected. After receiving the Fairphone 4, this will move from the Fairphone 3+ to the FP4 and the old SanDisk Ultra microSDXC 200 GB moves into the FP3+.


  • SanDisk Extreme® PRO microSDXC™ 400 GB Memory Card
  • SD™ Adapter for microSDHC™/SDXC™ Memory Cards

Tech Specs

Model: SanDisk Extreme® PRO microSDXC™ 400 GB + SD Adapter

Measurements: 0,1 x 1,5 x 1,1 cm
Weight: 9 g

Memory size: 400 GB

max. reading speed: 170 MB/s*
max. write speed: 90 MB/s*

* reading speed and write speed are depending from miscellaneous factors, among others the used device and the file size which will be read and/or written

Special Features

App Performance Class: A2
UHS-Standard: UHS-I
Standard Speed Class: UHS Speed Class 3
Video Speed Class: V30


The SanDisk Extreme Pro 400 GB was recognised by the Apple MacBook Air (2020) without reformatting after I inserted it into the card reader of the connected Anker PowerExpand Elite 13-in-1 Thunderbolt 3 Dock. After copying a backup of my old SanDisk Ultra microSDXC 200 GB to it, I inserted it into the card slot in the new Fairphone 3+. It was recognised without any problems here as well and has been used as a data storage device ever since.

Big Collection of Music Files on microSDXC

I generally listen to my music via MP3. Years ago, I had saved my CD collection in the highest possible quality as MP3. I also saved some CDs as WAVE (.wav). And since I use Apple iPhones and bought Apple music albums, I also have many albums in m4a format. These can be played on Android smartphones with the VLC player.

And because Apple announced in August 2021 that they will bring device-side image scanning technology to all iPhones and Macs with iOS 15 and macOS 12, I have exported my music collection to memory card and am preparing for the system change. This technology cannot be used only to protect the welfare of children, as is claimed. Security researchers around the world have been warning about such technology since 2019, which can be used to search for files of all kinds and put activists, journalists, etc. in danger of their lives in rogue states.

Photograph not on slide film but digital on microSDXC

I generally save photos from the smartphone camera on a memory card so that I don't lose any photos if the smartphone suddenly breaks down. This is not possible with the iPhone, so daily backups to local data media are mandatory if you want to be sure.

Backup of the Backup

The complete data I copy with regularity to an external hard disk drive because even a memory card can have a defect or could be ruined by a malfunction of device. Other issues can be software malfunction or ramsomware.


  • reliable
  • high performance


  • stated max. write speed hasn't reached in test reports from several pc magazines

I can't check the max. write speed without a measurement device but the most test reviews shows lower measurement values.
Reading speed and write speed are depending from miscellaneous factors, among others the used device and the file size which will be read and/or written.
More important as highest speed is reliability – so I am very pleased with this memory card!


This memory card has been doing its job reliably in my Fairphone 3+ since almost a month.

 Practical Tip

Some vendors are very carefully with their statements about the maximum size of memory cards or do not update their website.
For example Smartphones like the Samsung Galaxy Note or the BlackBerry Z10 had the capability to use memory cards with a size of 64 GB right from start.

It's your own risk if you buy a bigger sized memory card as the vendor recommends.
But in worst case use the microSDXC memory card with the SD Adapter in your digital camera or MP3 player or as a backup storage for the notebook.
Side benefit: because of the high performance of this microSDXC memory card you can make faster serial photo shoots depending from the capability of the camera model.


When it comes to speed, the Extreme Plus is the only alternative. The others are too slow for 4K/fast continuous shooting with the SLR camera (80–90 MB/s only theory)!

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