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
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4GB Kit 2 X 2GB DDR2 Memory for Dell Optiplex 755 760 GX280 Ultra Small Form Factor Desktop PC2-6400 240 pin 800MHz Non-ECC DIMM RAM (PARTS-QUICK Brand) at Amazon.com
8GB 4X2GB Dell OptiPlex 755 Series Desktop/PC DDR2 PC2-5300 RAM Memory at Amazon.com
Dell Optiplex 755 SFF Intel Core 2 DUO 3.16GHz 2GB RAM 160GB HDD Desktop PC | RecycledGoods.com
Dell Optiplex 755 PC Computer Tower Windows 10 Professional (Win 10) 4GB RAM 250GB
OFFTEK 2GB Replacement Memory RAM Upgrade for Dell OptiPlex 755 Series (Desktop Mini-Tower and Small Form Factor) (DDR2-6400 - Non-ECC) Desktop Memory at Amazon.com
Dell Optiplex 755 SFF - Intel Core 2 Quad 2.4GHz - 4GB RAM - 1TB HDD - Windows 7 Pro 64-Bit - WiFi - DVD/CD-RW USED - Walmart.com