Type: 3.5" SATA
Interface Type: Serial ATA
Spindle Speed: 7200 RPM
Width: 4.00 in
Depth: 5.787 in
Height: 1.028 in
Purchase a Seagate drive if your iMac originally came with a Seagate drive.
Purchase a Western Digital drive if your iMac originally came with a Western Digital hard drive.
The replacement hard drive needs to be the same brand as the original. This allows the heat sensor to be plugged in. The size of the drive does not matter.