I bought 2 of these at Ktech aka IMPC. One was much slower than advertised. Writing speed: 35.7 MByte/s Reading speed: 38.9 MByte/s 57.8GB in 1GB blocks The other one 'disappeared' from the USB port after 1.5GB of data written. Reproducible. Worked in a pure USB 2.0 port though. KTech aka IMPC offered me a refund after they had them tested at their supplier.