Crucial Technology CT3264AC53E 512MB SODIMM PC2-4200 DDR2 533MHZ 240PIN DIMM 1.8V CL4 Storage Capacity - 256 MB Technology - DDR2 SDRAM Form Factor - SO-DIMM 200pin Technology - DDR2 SDRAM Memory Speed -- 533MHz DDR2-533/PC2-4200