Review on KEXIN 64GB Micro SD Card Class 10, U3, MicroSDXC UHS-I C10 - High Speed Memory Card (3 Pack) by Stephen Schmidt

It was advertised as a U1 SD card (10MB/s write) but all three in my pack have been tested to write faster than 40MB/s (tested with Serial 100MB entry with Crystaldiskmark) which places it in the U3 category. The reading speed exceeded 80 MB/s. This was probably one of the few times I've bought an inexpensive microSD card that actually turned out better than advertised. Results may vary depending on the item purchased.