What does 55x or 150x in microSD cards mean?

Answer 1

Denotes maximum data transfer speed

By today's measure, sub 20X represents a standard speed, 20X to 40X is mid-high speed and over 40X is high speed. The chart below shows the relationship between the two figures.


8X = 1.2 MB/sec
12X = 1.8 MB/sec
20X = 3.0 MB/sec
25X = 3.8 MB/sec
30X = 4.5 MB/sec
40X = 6.0 MB/sec
60X = 9.0 MB/sec
66X = 10.0 MB/sec
80X = 12.0 MB/sec
90X = 15.0 MB/sec
133X = 20.0 MB/sec