After I wrote the post I started to think if they were fat32 or exfat when they arrived, but I remember trying to copy the 4.3GB ISO file and it failing saying that it can’t copy a large file, so they must have been Fat32, which is weird because they should have come formatted as exFat as standard because of the disk size.
I bought these directly from SanDisk themselves via their shop on Amazon so I don’t think they are used. They came in sealed original SanDisk packets with serial numbers, which I am going to try and check.
I read a few other posts about slow transfer speeds and someone suggested doing a full format rather than a quick format. Doing this changed the transfer speeds dramatically. The transfer still starts at 67MB/s but only drops to 20MB/s which I can live with, but this is nothing like the speeds SanDisk are claiming these drives can perform at.
