I purchased this product to use with my Surface Pro 4 and have been pleased with the performance, especially considering the price ($78) I paid. The read speed that I have experienced has been averaging around 60-70 Mb/s, a little shy of the manufacturer's stated read speed of up to 90 Mb/s; however, it is still fast enough that I have not noticed any issues with video playback, or with transferring files from the card. On the other hand, and perhaps the only downside of the card, the write speed I have seen averages only 10-15 Mb/s. The card will burst up to close to 20 Mb/s, but down-burst quickly, and sometimes stalls for 2-3 seconds between files when copying a large number of files to the card. In comparison, I recently purchased the Samsung EVO+ 256 GB Micro SD, and noticed that it does out perform the SanDisk, notably with the write speed (Samsung's write speed averages 70 Mb/s). The Samsung card cost me $200 (price match), a substantial difference for the extra 56 GBs . Verdict: the SanDisk 200gb Micro SD card is worth the money for the capacity, especially if the main objective is to free valuable HDD space. However, if one plans on using the card by frequently copying large amount of data (1gb+) to the card, and time is of the essence, it may not be the best option due to the slow write speed. Note: one issue that I recently have seen is that when playing videos from the card, my HDD space is reduced temporarily (until reboot), perhaps due to write caching (although I have write caching disabled).