This Seagate Expansion external drive is compatible with PCs and has a 3.5-inch form factor. The storage capacity of this unit is 120 GB, with an IDE interface. The product line for this unit is Momentus 5400.4 ST9120817AS, with an unknown write speed. This silver unit is an internal hard drive that is brand new and comes with one unit quantity. It is a type of external drive that can be used for storage purposes.