WD100EFGX-20PKSold as a pack of 20. Each drive spins at 7200 RPM and features a 6 Gbit/s interface rate. The drives have a 512 MB buffer and are rated for 1,000,000 hours MTBF. These internal HDDs are designed for NAS systems and can handle workloads up to 180 TB/year. The drives are suitable for small to medium business NAS environments.