I bought three of these and all three worked upon initial installation with no formatting. Using my notebook computer's built in SD card reader, I saw transfer speeds between 6 Mb writing and 14 Mb reading. This was doing a simple "copy / past" of all files on my old card that I had saved to my computer. These speeds are much slower than the stated maximum by the card manufacturer, but would be expected with over 12,000 small files like my example. The read / write times were close to 50% faster than those of my old 8 Gb class 10 SanDisk micro SD card, so there is definitely a performance gain with this updated card.All things considered, 16 Gb of storage on a Class 10 card from the leading manufacturer, and at $15 is a steal. I highly recommend this card.