Thunderbolt Duo 4TB for iMac as boot main drive

WD External Drives External Drives for Mac
2

Check the link below

Hope this can help

http://wdc.custhelp.com/app/answers/detail/a_id/1787/session/L3RpbWUvMTM2MTQwNjE1Mi9zaWQvUEE2UEZtamw%3D