[PeterStuer]

The original 2TB - 3TB - 4TB - 6TB Reds with the 'EFRX' suffix were CMR, the later ones with the 'EFAX' suffix are SMR drives.

[donatj]

Update: EFBX looks to be entirely CMR

Know anything about EFBX? SMR I assume? I literally have one arriving today to replace a disk in my single disk redundancy JBOD

The whole disk buying process was irksome because I up until WD shut them down always depended on HGST.

[PeterStuer]

If you mean the FFBX (I can't find any reference to EFBX models), the Red Pro series, those are CMS (and 7200rpm which is what the B stands for).