SanDisk Extreme Pro SDXC Card 64GB - 170MB/s V30 UHS-I U3 has a capacity of 64GB, is compatible with the UHS-I bus, and features a speed class rating of V30, which guarantees minimum write speeds of 30 MB/s. If your device does not support the V30 standard, this card also supports the U3 standard, which likewise guarantees minimum write speeds of 30 MB/s. Read speeds are supported up to 170 MB/s and write speeds max out at 90 MB/s. A built-in write-protect switch helps to safeguard against the accidental erasure of card data.