I put the card in my reading lamp (a muse cybook), just to be able to take my books with me ;-) 6000. She walks. She fast air: the previous SD (who died) was slow to the point that if you opened a new epub file, put the reading light several minutes to make its layout calculations. See over time how it ages. By cons, a star less for packaging: it was very hard to go out and to avoid damaging the memory card, I removed the package and I dropped (on the couch). To read other reviews, some (s) have spoiled the memory card at the time. So beware.