What does X mean on SD card?
The max read speed indicates how fast the data from the memory card can be read under ideal circumstances. On some cards, an x-rating value is displayed. The x-rating is based on the original data transfer speed of CD-ROMs (150 KB/s).
What does class 10 mean on a microSD card?

Class 10 is the fastest, suitable for “full HD video recording” and “HD still consecutive recording.” Class 2 is the slowest, suitable for standard definition video recording. Classes 4 and 6 are both deemed suitable for high-definition video recording.
What is V10 vs V30 SD card?
V6 Speed Class means that the minimum write speed of the memory card needs to reach 6MB/s, V10 is 10MB/s, 30 is 30MB/s, and so on. V60 and V90 can be applied to high resolution and high quality 8K video recording, and V30 can be applied to 4K resolution.
Is SanDisk Extreme Class 10?
Glance over both the SanDisk Extreme and Extreme Pro and you’ll notice the number 10 inside the letter ‘C. ‘ This shows they’re Class 10 SDs—the highest rating of a memory card—and indicates that they possess a minimum data transfer speed of 10 MB/s.

What are the classes of microSD cards?
The SD Association devised a way to standardise the speed ratings for different cards. These are defined as ‘Speed Class’ and refer to the absolute minimum sustained write speeds. Cards can be rated as Class 2 (minimum write speed of 2MB/s), Class 4 (4MB/s), Class 6 (6MB/s) or Class 10 (10MB/s).
Will a Class 10 SD card work in a Class 4 device?
All Class 2, Class 4, Class 6 and Class 10 SDHC cards are compatible with SDHC devices. Please note that if the device manual suggests a SDHC card of speed Class 4 as a minimum, the user should install a Class 4, Class 6 or Class 10 (faster) SDHC, NOT a Class 2 card as this may reduce performance of the device.
What is the difference between V10 and V30 SD card?
Is Class 10 same as V30?
So V6 is the same as Class 6, V10 is the same as Class 10 and U1, and U3 is the same as V30!
What’s better SanDisk Ultra or extreme?
The primary difference between SanDisk Ultra and SanDisk Extreme cards is video recording capabilities. SanDisk Ultra performs best with 1080p HD video recording, while SanDisk Extreme can record 4K video. SanDisk Ultra cards do not have read or write speeds fast enough for 4K video recording.
What is better SanDisk Extreme or pro?
If the price is not the most important factor for you, SanDisk Extreme Pro is better than SanDisk Extreme in the aspects of data speed, capacity options, and compatibility. With a SanDisk Extreme Pro microSDXC card, you can enjoy the maximum read speed of 170MB/s, which can save you more time.