The "U3" means it can handle sustainable writes of at least 30 megabytes per second, which is required for recording 4K video up to 60 frames
per second or for taking a burst of RAW photos with an SLR camera.
However, some reviews of these PNY SD cards talk about data and performance loss, which makes me nervous about using in our SLR camera.
We used SanDisk Extreme Pro SD cards in our SLR camera, and love it.
As long as you buy from a reputable seller (look for the actual seller on Amazon.com) and avoid counterfeit products, SanDisk is our recommended pick for high performance SD cards for SLR cameras.