Western Digital 4TB WD Red Plus NAS Internal Hard Drive HDD - 5400 RPM, SATA 6 Gb/s, CMR, 256 MB Cache, 3.5" -WD40EFPX. Compatible Devices NAS System. Available in capacities ranging from 1-14TB(1) with support for up to 8 bays | (1) 1MB = 1 million bytes, 1GB = 1 billion bytes, and 1TB = 1 trillion bytes.
eBay