My $5.95 Delkin Devices "Select" 32-GB SD cards are now in hand.
Across the bottom of the package says "Read 100MB/s - Write 30MB/s"
The information on the back says 660X ; I still haven't figured out the significance of this X business, but I do believe the larger the number the better.
The “x” designation is a result of the marketing geniuses. The quantity 1x represents 150 kb/s, so 600x is the same as a 90 MB/s rating (600 x 150 = 90,000). This number typically represents the “read” speed, which is generally higher than the “write” speed.
I vaguely recall that the “base” of 150 kb/s was somehow related to the specification of CD-ROM.

