Western Digital Red Pro  4TB 3.5-Inch 7200rpm 64MB Cache NAS Hard Drive (WD4002FFWX) Available in large capacities with support for 1-16 bays Enhanced reliability with 3D Active Balance Plus and error recovery controls with NASware 3.0 Extended drive testing to ensure each drive is tested for extended reliable operation Vibration & Shock protection Package includes a hard drive only - no screws, cables, manuals included. Please purchase mounting hardware and cables separately if necessary. Ships in WD-certified box for safe transit during shipping