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 64 X 4) COMPATIBLE WITH DFI AK74-EN Motherboard Lifetime Warranty . The "512MB SDRAM DIMM 168 Pin 133Mhz PC133 FOR DFI AK74-EN Motherboard 512MB" is best product for you. We recommended 512MB SDRAM DIMM 168 Pin 133Mhz PC133 FOR DFI AK74-EN Motherboard 512MB