**Update 6.24.14**My 128 GB card stopped allowing writes via any of my card-readers on a Windows PC--either when it was inside any of several full-size SD card adapters (with the write-protect tab in either position) or plugged directly into the microSD slot of the reader.  MicroSD cards have no write-protect tab, so I was quite surprised and worried by this.  After failing to find any workable solution by searching online, I finally put it in my Chromebook and created a new folder on it there, then stuck it back in my Windows PC and it no longer gave me a write-protect error.  If anyone has a similar problem, I'd recommend doing something similar by putting it in any other PC, laptop, camera, etc you have available and try writing to it there.----------------------------------------------This portion of my review is necessarily being written as an update to my original review of the 64 GB version of this card, since Amazon disallows multiple reviews for what they consider the same item.  This portion concerns the 128 GB version of this card:I don't need a fast card, so the speeds on this card were not that important, besides which my test PC is not exactly high-end. Therefore I didn't count off for the speed results I got below, using a USB 2.0 card adapter, but I thought they might be relevant to some readers. While the card did reach the Class-10 and/or UHS-I requirements, it came in at under 2/3 of the claimed "read speeds up to 30 MB/s for fast file transfer."  Then again, running on a second PC using a different USB 2.0 card reader, none of the speeds even hit 5 MB/s, so this seems to be highly system-dependent.I only just got the card this week, and so far it works on *select* SDXC-compatible devices and exFAT-compatible operating systems:  some SDXC-compatible devices, such as the Panasonic HDC-TM40, do not allow cards larger than 64 GB (for whatever reason); this was stated in the manual, and I've confirmed this card is recognized as broken/corrupt/unusable in that device, whereas 64 GB exFAT cards work fine.  The 128 GB works fine (with original exFAT formatting) in my Toshiba Excite 7.7 Android tablet, and (predictably) not at all in my non-SDXC-compatible Galaxy Note 2 (though it possibly would if reformatted to FAT32, since a 64 GB card in FAT32 works fine there).I'll update my review to reflect any problems, issues, etc that I notice in the coming days & weeks.-----------------------------------------------------------------------CrystalDiskMark 3.0.3 (C) 2007-2013 hiyohiyoCrystal Dew World : [url removed as per Amazon rules]-----------------------------------------------------------------------* MB/s = 1,000,000 byte/s [SATA/300 = 300,000,000 byte/s]Sequential Read : 18.694 MB/sSequential Write : 11.921 MB/sRandom Read 512KB : 18.502 MB/sRandom Write 512KB : 0.680 MB/sRandom Read 4KB (QD=1) : 3.339 MB/s [ 815.1 IOPS]Random Write 4KB (QD=1) : 1.581 MB/s [ 386.1 IOPS]Random Read 4KB (QD=32) : 3.151 MB/s [ 769.4 IOPS]Random Write 4KB (QD=32) : 1.564 MB/s [ 381.8 IOPS]Test : 1000 MB [G: 0.0% (0.0/119.1 GB)] (x5)Date : 2014/04/24 16:53:49OS : Windows XP Professional SP3 [5.1 Build 2600] (x86)-------------------------------------------------------------------------------------------------------------------------------The following is my original review of the 64 GB version of this card, published April 24, 2013:This is a high-quality card.  I've used it in a variety of devices, through multiple readers on different pcs, in an HD camcorder using a micro to full-sized SD adapter, and I've never once had a problem with it.  It even works at full capacity in *some* microSDHC-only devices once its reformatted to FAT32 (such as my SanDisk Clip+ FLAC player and supposedly even PSPs via a proper adapter, though I haven't yet tested my PSP).  I keep anticipating someone coming out with a card with equal or better capacity and speeds at a comparable price, but I haven't seen one yet.  If these were cheaper, I'd have several by now.Make sure your device can handle micro or full-sized SDXC cards, or is one of those rare gems that state they support only as high as SDHC but have been tested to work with SDXC cards such as this one once they've been manually reformatted to FAT32.