This is the one I just ordered, U3 rated at 90MB/s read, 80MB/s write. It benchmarks very closely to the newer Pro+, but $20 cheaper. https://www.amazon.com/Samsung-Class-Adapter-MB-MG32EA-AM/dp/B014W1ZKX4/

This is the one currently in my phone, the one that makes the camera shutter and photo gallery laggy: https://www.amazon.com/gp/product/B010Q588D4/ Read speeds are similar to the Samsung Pro, but write is only 15MB/s, hence the U1 rating.