4GB 667MHz DDR2 ECC CL5 DIMM (Kit of 2)...Standard 256M X 72 ECC 667MHz 240-pin Unbuffered DIMM (SDRAM-DDR2, 1.8V, CL5). ValueRAM KVR667D2E5K2/4G is a kit of two 256M x 72-bit 2GB (2048MB) DDR2-667 CL5 SDRAM (Synchronous DRAM) ECC memory modules. Total kit capacity is 4GB (4096MB). The components on each module include eighteen 128M x 8-bit DDR2-667 SDRAM in FBGA packages. Each 240-pin DIMM uses gold contact fingers and requires +1.8V.