This is a 4TB (Terabyte) Hard Drive. Up until recently, 4TB was unheard of for a High Quality Security Hard Drive. This is a state-of-the-art hard drive manufactured specifically for security DVRs and NVRs. These hard drives are not desktop hard drives. Desktop drives cannot handle the abuse that a typical DVR puts on a hard drive. Security DVRS and NVRs are always on and run at high temperatures. In order for you to have the most accurate recordings, you will need a Security Hard Drive such as this one. These are manufactured in such a way that it prevents frame loss and is very durable and long-lasting. With data transfer speeds of up to 6GB/s, you will be rest-assured your recorder is saving to a high quality drive.