Western Digital WD Red 4TB NAS Internal Hard Drive - 5400 RPM Class, SATA 6 Gb/s, 256 MB Cache, 3.5" Specifically designed for use in NAS systems with up to 8 bays Supports up to 180 TB/yr workload rate Rate is defined as amount of user data transferred to or from drive. Workload Rate is annualized (TB transferred times (8760/recorded power-on hrs)). Workload Rate will vary on hardware/software components NASware firmware for compatibility Small and home office NAS systems in a 24/7 environment model : Western Digital WD Red 4TB NAS Internal Hard Drive - 5400 RPM Class tag : Internal Hard Drives