Western Digital Red Pro NAS 4TB 3 5" SATA 6GB/s 7 2K 64MB HDD WD4001FFSX
WD Red PRO 4TB NAS Desktop Hard Drive WD4001FFSX or WD4003FFBX or WD4005FZBX
WD Red Pro NAS Hard Drive WD4001FFSX - Hard drive - 4 TB - internal - 3.5" - SATA 6Gb/s - 7200 rpm - buffer: 64 MB - for My Cloud EX4 - Walmart.com - Walmart.com