Western Digital WD44purz Purple 4TB Hard Drive – 3.5′ Internal – SATA (SATA /600) -3-Year Limited Warranty

Western Digital WD Purple 4TB 3.5′ Surveillance HDD 5400RPM 64MB SATA3 6Gb/s 150MB/s 180TBW 24×7 64 Cameras AV NVR DVR 1.5mil MTBF 3yrs

Key Features
Storage Capacity: 4 TB
Buffer: 256 MB
Wireless LAN: No
Drive Interface: SAT