The Western Digital 2TB SATA Purple Internal Hard Disk is a 3.5" internal hard disk drive that belongs to the company's Purple line of HDDs, which are designed specifically for use in surveillance systems.

Some of the key features of this hard drive include:

• SATA III 6 Gb/s interface for fast data transfer rates
• 64 MB cache to improve performance
• AllFrame technology, which helps to reduce video frame loss and improve playback quality in surveillance systems
• TLER (Time-Limited Error Recovery) technology, which improves drive reliability by reducing the drive's error recovery time
• Support for up to 32 cameras per drive

Overall, the WD 2TB SATA Purple Internal Hard Disk is a high-quality and reliable hard drive that is well-suited for use in surveillance systems where high-quality video recording and playback are essential, but a smaller storage capacity is needed.