HGST (Hitachi owned by Western Digital) 1TB 2.5". This is a used and fully tested hard drive taken from a recycled MacBook or MacBook Pro. The testing process on this drive involves low-level erasing the disk and cloning a disk image of a clean OS install onboard.
If this process works without abnormal pausing or noise then the drive is used to boot a test machine. The drive built-in diagnostics are then checked.
Please note that the pre-loaded version of MacOS on this disk is to validate testing and if you do not own a legal copy of this operating system for the machine you plan to use this drive in, you should erase the disk before use.