Green WDS240G1G0A 240GB is an SSD type hard drive which can fit 240 GB of data. The form factor is 2.5" which is standard for SSD drives.
From Amazon
Western Digital 2.5-Inch 240 GB Solid State Drive - Green
Clove Technology
Western Digital Green 2.5" 240 GB Serial ATA III
Athema Services
western digital wd green ssd 2.5" - 240gb **new retail** wds240g1g0a -