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Amazon.com: Western Digital WD40EFRX WD Red NAS Hard Drive - Hard drive - 4 TB - internal - 3.5 inch - SATA 6Gb/s - buffer: 64 MB - for WD My Cloud EX2, EX4 : Electronics
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Western Digital Red NAS 4TB 5400RPM SATA 6Gb/s 64MB Cache 3.5" Enterprise Class Hard Drive - WD40EFRX - Drive Solutions
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