The Hynix Desktop RAM 4GB kit 2RX8 PC2-6400U-666-12 Memory is a DDR2 RAM module with a total capacity of 4GB spread across two 2GB modules. It has a DIMM form factor, 240 pins, and operates at a bus speed of PC2-6400 (DDR2-800). Manufactured in Korea, Republic of, this RAM kit is a reliable and high-quality option for upgrading your computer's memory capacity.