Product Detail 512MB PC133 SDRAM DIMM SDRAM (Synchronous DRAM). 133 Mhz (backward compatible with PC 100/66). Operating voltage: 3.3V. 168 PIN Dimm (Dual In-Line Memory) Compatible With Desktops Lifetime Warranty . The "512MB SDRAM DIMM 168 Pin 133Mhz PC133 DESKTOP MEMORY" is best product for you. We recommended 512MB SDRAM DIMM 168 Pin 133Mhz PC133 DESKTOP MEMORY