4GB DDR3 Memory Upgrade for Dell Optiplex 780 DT/MT/SFF PC3-8500 240 pin 1066MHz Desktop RAM (PARTS-QUICK Brand) at Amazon.com
OFFTEK 4GB Replacement Memory RAM Upgrade for Dell OptiPlex 790 (Desktop) (DDR3-10600 - Non-ECC) Desktop Memory at Amazon.com
Amazon.com: Dell OptiPlex 780 USFF Desktop Intel Core 2 Duo 3.0 GHz 4 GB RAM 250 GB HD DVD Win Pro 32-Bit (Renewed) : Electronics
Dell OptiPlex 780 Small Form Factor - iFixit
Dell Optiplex 780 Windows 10 Pro Desktop PC Tower Core 2 Duo 3.0GHz Processor 8GB RAM 500GB Hard Drive DVD-RW Wifi with a 22" LCD-Used Computer - Walmart.com