that's the touted min write speed, i'm willing to bet it's higher than 10. Most class 10 SDHC are at least ~14-18MB/s sequential write (I think the sony's somewhere around there).
edit: nvm, it seems they don't even hit the 10MB/s mark (the only product reviews I found tested it for 1MB files, so ymmv), they're hovering at 9.9 ish :|, man those are slow SDHC... If buying these for "class 10" performance, might as well pick up a later era class 6, which easily exceeds 10MB/s.
the min 10MB/s for class 10 isn't even true most of the time if counting small 4KB files 😉 (hey what if you want to store tons of txt files?), so I really don't like how the "class 10" rating is thrown around so much.
still a good deal for cheap storage or low/normal bitrate HD.