"Fast enough"

I purchased this card to use in a GoPro Hero 3. It keeps up with the 1080p video being wrote to it. I don't know if it would do 4k video, but 16GB wouldn't be enough for that type of quality either. Bravo SanDisk.

"Great storage and fast speed for copying Digital SLR photos and MP3s."

I figured out why my old microSD card died on me. When I plugged in my old Android phone at work, the antivirus software of my laptop wanted to scan the whole thing every time. I was plugging it in to charge it, but the constant reads wore out the flash. My new Android phone mounts as a CD drive (instead of the entire thing). I can only see the phone if I unmount my CD drive. This is perfect for charging at work now. Be careful with virus scanners if you have an Android phone that auto mounts your entire phone's Micro SD!