The ProMOS PC2-6400U-666-12-D0 1GB RAM consists of two 512MB DDR2 SDRAM modules with a total capacity of 1GB. These DIMM modules have a bus speed of PC2-6400 (DDR2-800) and are designed for high performance in computers and networking devices. With 240 pins and a capacity of 512MB per module, this RAM is a reliable choice for upgrading or replacing existing memory modules in order to improve system speed and efficiency. These have been tested and cleaned.