Transcend Information, Inc. super high capacity 4GB DDR333/400 ECC Registered Memory Module (P/N: TS512MDR72V3/4T) is the latest memory you won't see in your desktop. That's because it only measures 1.2 inches high, making it the ideal low-profile memory for high-end computing systems, such as the IBM eServer xSeries 326, Sun fire V20z/V40z and Compaq Proliant DL145/DL585 server. The 4GB DDR333/400 ECC Registered memory module consists of 256Mbx4 stacked (512Mbx4) original brand DDR TSOP chips. The eight-layer PCB used for Transcend's 4GB modules meet the highest specifications by minimizing noise signal disturbance and enhancing overall performance. What that means to you, is twice the memory occupying the same space. Every single Transcend memory module undergoes rigorous laboratory testing and comes with a lifetime warranty.