Western Digital WD1004FBYZ Lenovo System X IBM M4 Series 1TB 3.5" 7200 RPM 128MB Cache SATA3 6GB/s HDD Hard Disk Drive with Swap Tray 81Y3867 81Y9806 81Y9807.WD Model Number: WD1004FBYZ-23YCBB0Lenovo Part Number: 81Y3867Lenovo Option Part Number: 81Y9806 P181Y9806Lenovo FRU Part Number: 81Y9807IBM Swap Tray Part Number: 69Y5342Compatible Part Numbers: 00AJ525 11S00AJ525Compatible Models: Lenovo System X IBM M4 ServersSpecifications:Form Factor: 3.5"Series: Server HDDInterface: SATA III, Serial ATA-600 (6.0 GB/s)Cache: 128MBCapacity: 1TBRPM: 7200 RPM