HGST Deskstar 3.5-Inch 4TB CoolSpin SATA III 6Gbps Internal Hard Drive Kit 32 MB Cache 3.5 Internal Bare or OEM Drives (0S03359) Hard disk drive with a large storage capacity of 4TB SATA III 6 Gbps interface The 3.5" SATA III hard drive utilizes CoolSpin technology to optimize the motor speed of the drive so as to use less power, quietly operate, and still maintain a high-standard of performance Designed to be more eco-friendly than other hard drives on the market, this drive does not use halogen and is power-efficient Compatible with Windows or Mac Systems