4GB 2X2GB Memory RAM for Dell OptiPlex 755 Mini Tower 240pin PC2-5300 667MHz DDR2 DIMM Black Diamond Memory Module Upgrade System Specific Memory - Newegg.com
8GB (4GBx2) Team High Performance Memory RAM Upgrade For Dell OptiPlex 755 Series (Desktop Mini-Tower and Small Form Factor). The Memory Kit comes with Life Time Warranty. at Amazon.com
Dell Optiplex 755 PC Computer Tower Windows 10 Professional (Win 10) 4GB RAM 250GB