Worked as I expected (SanDisk Extreme 128gb); slightly faster card than the SanDisk Ultra 128gb that I was using as a storage drive for my Rasp Pi4.

None, except beware of on-line vendors offering discounted versions of these SD cards (see below).

**Beware of heavily discounted storage media being offered on-line** I purchased the SanDisk Extreme 128gb card from Memex, reformatted it using Linux gparted tool, to Ext4 filesystem. I then used Clonezilla to restore my Rasp Pi4 production drive SD card (a SanDisk Ultra 128gb) to the SD Extreme card from Memex. The Extreme version card with the restored Pi4 O/S, when inserted into my Pi4, performed slightly better than the Ultra version card, as expected. Boot was faster, as were installing O/S updates. For a comparision, I also purchased the same SanDisk Extreme 128gb card online from a very large international retailer, for $20 less than the Memex price. Six weeks later that other SD Extreme card was delivered. I noticed the vendor's address on the shipping envelope was in China. When I opened the package, the SD Extreme card from China (in a SanDisk-branded package), had already had the thin plastic seal on the back of the little plastic container, removed. When I plugged that card into my main Linux box, the first thing I noticed was that it had been formatted to Fat32. Normally these cards ship as formatted to Exfat. I attempted to reformat the card to Ext4 so it would be usable for My Rasp Pi4. It (the reformat) failed. The error message indicated the GPT backup partition table was corrupt. After several hours of using Linux gdisk, Linux gparted, and Linux dd (to zero out the card), I could not successfully reformat that card without getting a corrupted GPT backup partition table. I was also unable to create a GPT partition table successfully on that drive as well. And when, as a last attempt, I tried to run Clonezilla to restore my Pi4 image from the SanDisk Ultra card, to this defective Extreme card, Clonezilla threw up its arms to say, destination (target) disk is not as large as the source disk. And finally, just for fun, I attempted to format this defective Ultra card in NTFS. That failed too. It indicated the superblock was defective. (using Linux gparted). So, lesson learned. I concluded that the e-tail order card was either a fake imitation one, or it had failed inspection at the SanDisk manufacturing plant; so it got sold off to some shyster flipper, who then resold it (to me) via the e-site from a large international retail outfit. Buyer beware. Low price may certainly be an indicator of counterfeit or defective merchandise.