This is an SSD drive with a 250 GB storage capacity. The form factor of this SSD is 2.5".
From Amazon
WD Blue WDS250G1B0A 250 GB Internal SSD Solid State Drive, SATA 6 GB/s 2.5 Inch
Clove Technology
Western Digital Blue PC 2.5" 250 GB Serial ATA III
Compadvance
WESTERN DIGITAL Wd Blue Pc Ssd Wds250G1B0A