The product is a lot of four Western Digital WD Blue 500GB SATA III 2.5" hard drives with a rotation speed of 5400 RPM and a cache size of 16MB. These internal laptop drives are compatible with laptops and PCs, and come in a form factor of 2.5 inches. The drives have a storage capacity of 500GB and an interface of SATA III, with a transfer rate of 6 Gbps. They are designed for HDD storage format and feature a WD Blue product line. The item length is 100mm, height is 7mm, and width is 69.85mm. The drives are in silver, black, and green colors.