4GB [2x2GB] DDR2-533 (PC2-4200) RAM Memory Upgrade Kit for the Dell Optiplex GX520 Desktop (Genuine A-Tech Brand) 4GB [2x2GB] DDR2-533 (PC2-4200) RAM Memory Upgrade Kit for the Dell Optiplex GX520 Desktop 100% Genuine A-Tech Brand Memory 2GB DDR2-533 PC2-4200 Non-ECC Unbuffered 240 Pin 1.8V CL=4 Memory 128X8 Limited Lifetime Warranty High Quality Ram specifically designed for the Dell Optiplex GX520 Desktop