For 64GB-1TB: A2 performance is 4000 read IOPS, 2000 write IOPS. For 32GB: A1 performance is 1500 read IOPS, 500 write IOPS. Results may vary based on host device, app type, and other factors. UHS Speed Class 3 (U3) designates a performance option designed to support real-time video recording with UHS-enabled host devices. Video Speed Class 30 (V30), sustained video capture rate of 30MB/s, designates a performance option designed to support real-time video recording with UHS-enabled host devices. See www.sdcard.org/consumers/speed. Comparison based on internal testing of SanDisk Extreme® microSDXC™ UHS-l card, versus current UHS-l cards with 100MB/s stated performance. Results may vary based on host device, file attributions, and other factors. The most intense video-recording use in mobile today is recording 30 frame per second, 4K video; the Mobile Extreme card had no trouble with that, either. Compatible device required. Full HD (1920x1080) and 4K UHD (3840 x 2160) support may vary based upon host device, file attributes, and other factors. See www.sandisk.com/HD

SanDisk Extreme 64GB MicroSD Card Review | PCMag SanDisk Extreme 64GB MicroSD Card Review | PCMag

In most mobile use cases, sequential read and write speeds are a lot more important than random read and write speeds.Copying and playing photos, videos, and music all use sequential reads and writes, and that's what most people do with their microSD cards. Random reads and writes are more common when running an OS or application off the card, a much less common use. That said, the SanDisk Extreme card also had some of the best random read and write speeds in our group, both on the phone and on the laptop.Thebig differences came when I was copying files from the laptop to the card, a common thing you'd do if you want to play movies on your phone.As you can see in the chart below, the SanDisk Extreme and Lexar 633x cards were much faster than any of the competitors. The Galaxy Note 3's SD card speeds seem to max out at around 20MBps both reading and writing. Only the Extreme card hit both limits.

MicroSDXC Memory cards | Argos MicroSDXC Memory cards | Argos

Get faster app performance for an outstanding smartphone experience thanks to the SanDisk Extreme® microSD card’s A2 7Specification. Capture fast-action photos or shoot 4K UHD video 2 with write speeds of up to 130MB/s. 9The SanDisk Extreme® microSDXC™ UHS-I Card lets you shoot more and faster. The SanDisk Extreme outperformed both the similarly-priced Leef Pro and the more expensive Lexar 633x, as well as slower SanDisk Mobile Ultra and Kingston Class 4 cards we were using to compare. For 256GB-1TB: Up to 190MB/s read speeds, engineered with proprietary technology to reach speeds beyond UHS-I 104MB/s, requires compatible devices capable of reaching such speeds. Up to 130MB/s write speeds. For 128GB: Up to 190MB/s read speeds, engineered with proprietary technology to reach speeds beyond UHS-I 104MB/s, requires compatible devices capable of reaching such speeds. Up to 90MB/s write speeds. For 64GB: Up to 170MB/s read speeds, engineered with proprietary technology to reach speeds beyond UHS-I 104MB/s, requires compatible devices capable of reaching such speeds. Up to 80MB/s write speeds. For 32GB: Up to 100MB/s read speeds; up to 60MB/s write speeds. Based on internal testing; performance may be lower depending upon host device interface, usage conditions, and other factors. 1MB=1,000,000 bytes.