j uses many USB key I found the normal transfer rate, no writing of problems. The format is surprising, but ultimately quite handy although it should be a little more space than for Microcard! They also lose less easily -for I lend these keys with software c is the price that made me the favorite key. (Purchase of 10 keys) The only problem is the transportation time, but they are still some arrivals exceeding 5 days the maximum allowed.