Review on Reliable and High Performance Transcend 256GB SDXC/SDHC 300S Memory Card - TS256GSDC300S by Jerry Frey

This is an old technology with very slow writing. You get what you pay for, but it works well and the 512GB SD card storage is very handy. Hard to find at this price. Be prepared for slow writes - typically only 10-15MB/s. But it works for me as I usually only write files to this card once and then read them back and that's fine. My laptop has a good SD card slot which makes them very handy. I've used 128GB and 256GB cards but 521GB is great. (Of course, as always, for security reasons, you should back up your files to a different drive, card, etc.) If I run into problems I'll come back and update, but so far so good. Works perfectly.