OFFTEK 512MB 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
A-Tech 8GB (4X 2GB) Max Memory RAM Kit for Dell OptiPlex 755, 745, 740, (MT, DT, SFF) - DDR2 667MHz PC2-5300 Non-ECC DIMM Upgrade at Amazon.com
Dell Optiplex 755 PC Computer Tower Windows 10 Professional (Win 10) 4GB RAM 250GB
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 SFF Intel Core 2 DUO 3.16GHz 2GB RAM 160GB HDD Desktop PC | RecycledGoods.com