Toshiba 4TB S300 Surveillance HDD - 3.5' SATA Internal Hard Drive Supports up to 64 HD cameras at a 180TB/Year workload (HDWT720UZSVA) : Amazon.co.uk: Computers & Accessories
Seagate Surveillance ST4000NM0035 Hard Disk 4TB 4000GB SATA 3,5 " DVR Computer | eBay