Western Digital Purple 4TB Surveillance 3.5 Inch SATA 6 Gb/s Hard Disk Drive with Allframe 4K Technology - 180TB/yr, 64MB Cache, 5400rpm - WD40PURZ : Amazon.co.uk: Computers & Accessories
WD Purple 4TB Hard Drive for Video Surveillance - Intellipower SATA 6 Gb/s 64MB Cache 3.5 Inch - WD40PURX : Amazon.co.uk: Computers & Accessories