Answer to "Compatible SSD Drive other than OWC"At this writing (late 2018), MCE Technologies at store DOT mcetech DOT com has a range of 3rd-party replacement SSDs for the Mac Pro up to 2 TB. I got their 1 TB (non-NVMe) version quite some time ago to replace the original 256GB Apple SSD, and it dropped right in with no hassles. The drive shows up in System Information as a Kingston SHPM2280P2/960G. If I were to do it again today, I’d get the 2 TB NVMe version. I have also seen genuine Apple OEM SSDs on eBay. One vendor is Bloomax. MCE’s are cheaper and claim to be every bit as fast as OEM.