How to Upgrade Memory in a 21.5-inch or 27-inch iMac (Mid 2010) - YouTube
Avarum 16GB Kit (2x8GB) DDR3L 1333MHz RAM for Apple MacBook Pro (Early/Late 2011), iMac (Mid 2010 27", Mid 2011 21.5"/27"), Mac Mini (Mid 2011) | PC3-10600 SODIMM 204-Pin Memory Upgrade - Newegg.com
iMac Intel 27" Mid 2011 EMC 2429 - used original spareparts for Macs
I recently purchased 2011 21.5 iMac (Mid-2011) and I'm obsessed. : r/mac
iMac 27" 2.7GHz (Mid 2011) | mac of all trades
16GB (4X4GB) RAM Memory FOR Apple iMac "Core i7" 3.4 27-Inch (Mid-2011) A33 | eBay
A-Tech 8GB RAM for Apple MacBook Pro (Early/Late 2011), iMac (Mid 2010 27 inch 4-Core, Mid 2011 21.5/27 inch), Mac Mini (Mid 2011) | DDR3 1333MHz PC3-10600 204-Pin SODIMM Memory Upgrade Module at Amazon.com
A-Tech 32GB (4x8GB) RAM for Apple iMac (Mid 2010 27 inch 4-Core, Mid 2011 21.5/27 inch) | DDR3 1333MHz PC3-10600 204-Pin SODIMM Memory Upgrade Kit at Amazon.com
Amazon.com: Timetec 32GB KIT(4x8GB) Compatible for Apple DDR3 1333MHz PC3-10600 CL9 for iMac (Mid 2010 27 inch, Mid 2011 21.5/27 inch) SODIMM Memory Module MAC RAM Upgrade for iMac 11,3 / iMac 12,1 / iMac 12, 2 : Electronics