The Hynix 512MB 1RX8 PC2-4200U-444-12 Internal Memory is a set of two DDR2 SDRAM modules with a total capacity of 512MB each. These modules are designed for high-performance computing, with ECC memory features for error correction. The memory modules have a form factor of DIMM, with 240 pins and a bus speed of PC2-4200 (DDR2-533), this memory unit is a reliable and efficient choice for upgrading or replacing existing computer memory modules.