Its going back because it doesn't meet spec.Tested with  H2TestW, write speed is only 9.69 MB/s. Read speed is good at 18.80 MB/s. (although Sandisk claims up to 30MB/s)Meanwhile, a class (10) 32GB Transcend SD card I have writes at 15.30 and reads at 18.20.I also have a few class (6) 4GB Sandisk microSD cards writing at 15.40 and 15.50. Reading speed is 18.40 and 18.30.I also have a class (4) Kingston card that beats this class 10 Sandisk.