This is External 2.5" IDE SATA HDD Anti-Static Box.
It is made of PP (Polypropylene) plastic, which is marked by damp proofing, dust-proofing, skid-proofing, anti-shock, anti-vibration and static-free. So it can give your 2.5" SATA/IDE hard disk all-around protection.
It can contain 2 hard disk in one case, convenient.
You can name the box contained different hard disk with a label. Thus, you can tick out the one you want easily.