The 250GB (2nd Gen) and 1TB (2nd Gen) Expansion Cards give you the performance of an internal drive with the flexibility of an external one. With a USB 3.2 Gen 2 interface, both the 1TB (2nd Gen) and 250GB (2nd Gen) cards reach 1000 MB/s read and 800 MB/s write speeds. Both are fast enough to run apps and even boot an operating system from, and you can plug them into other computers for high-speed file transfer.