MicroSD Cards explained

What is UHS SDHC SDXC U3 V30

  • Premium memory solution for sports camcorders, tablets, and smartphones
  • Quickly captures, stores, plays back, and transfers media files, including 1080p full-HD, 3D, and 4K video
  • UHS-I technology

Form Factor


microSDHC (Secure Digital High Capacity) SDA 2.0 specification.

Can store between 4GB and 32GB, but can only be used in devices compatible with the SDHC format.


microSDXC (Secure Digital eXtended Capacity) SDA 3.0 specification.

The latest type of memory card released in 2010 which meets the demands of FULL HD recording in terms of capacity and speed.

Storage sizes range between 64GB and 2TB.


UHS Speed Class (UHS Bus)

10 MB/s SDHC Speed Class 10.svg Class 10 (C10) UHS Class 1.png Class 1 (U1) Video Speed Class 10.png Class 10 (V10) Full HD (1080p) video recording and consecutive recording of HD stills.
30 MB/s - UHS Class 3.png Class 3 (U3) Video Speed Class 30.png Class 30 (V30) 1080p and 4K video files at 60/120 fps (UHS bus)
60 MB/s - - Video Speed Class 60.png Class 60 (V60) 8K video files at 60/120 fps (UHS bus)
90 MB/s - - Video Speed Class 90.png Class 90 (V90)



UHS-1 - Specification defines two bus architecture options for up to 50MB/s (UHS-50) and 104MB/s (UHS-104) data transfer rates.

UHS-II - Specified in version 4.0, further raises the data transfer rate to a theoretical maximum of 156 MB/s (full duplex) or 312 MB/s (half duplex).

UHS-III - Version 6.0, released in February 2017, added two new data rates to the standard. FD312 provides 312 MB/s while FD624 doubles that. Both are full-duplex.

So lets look at cards I use, this Lexar came with the 4K DJI mavi pro drone, but I am sceptical about it's effectiveness. And this is whyat made me write this page to help everyone.


Lexar® High-Performance 633x micro SDHC

Lexar® High-Performance 633x microSDHC LSDMI256BBNL633A

Lexar Class 10 UHS-I technology  for a transfer speed up to 95MB/s (633x)*, but does not say if this is read or write.

The Lexar is clearly stating it is C10 / UHS-1, and not ideal for 4k.




SANDISK EXTREME PLUS UHS Speed Class 3 (U3) performance up to 100MB/s read / 90MB/s write speed, C10, U3, V30 (video speed).


I am confused to the term UHS-1 yet also includes (U3) !!


So which of the two cards above are faster. They both claim similar write speeds, but I am inclined to go by symbols such as the U3. But the new XC 1 with an A1 looks to be a future choice.


Additional info on SDXC cards and host devices
- SDXC host devices can use and support SD, SDHC and SDXC memory cards.
- SDHC host devices can use and support both SD and SDHC memory cards.
- SDHC memory cards can be used with SDHC and SDXC host devices.


SD Memory Card Formatter 5.0 for SD/SDHC/SDXC


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