HP 4GB (1x4GB) Single Rank x4 PC3-12800 (DDR3-1600) Registered CAS-11 Memory Kit. Component for: PC/Server, Internal memory: 4 GB, Memory layout (modules x size): 1 x 4 GB, Internal memory type: DDR3, Memory clock speed: 1600 MHz, Memory form factor: 240-pin DIMM, CAS latency: 11, ECC