Single Bulk Pack WD Green WD20NPVX 2 TB SATA 6 Gb/s 8 MB cache IntelliPower 2.5-inch internal 15 mm hard drive. WD Green WD20NPVX hard drives are designed for use in systems that require cool and quiet operation, as secondary drives in PCs, for external enclosures and other applications for which low noise and low heat are beneficial. These earth-friendly 2.5-inch hard drives are ideal for use whenever energy efficiency is needed.