iMac RAM for Model 11.2 to 12.2 | DDR3-1066MHz | 4GBx2 | MacMemory.com
Install memory in an iMac - Apple Support
OWC 16GB (2x8GB) ram Upgrade PC3-12800 DDR3L 1600MHz sodimm 204 Pin CL11 Memory Upgrade Kit Compatible with Late iMac, Mac Mini, and MacBook Pro Computer at Amazon.com
CMS 16GB (4X4GB) DDR3 10600 1333MHZ Non ECC SODIMM Memory Ram Upgrade Compatible with Apple® iMac Core I5 2.5 21.5-Inch (Mid-2011) - A28 at Amazon.com
iMac RAM Models 11.3 (i5 and i7 only) to 12.2 (8GBx4) | MacMemory.com
Memory Upgrades for Apple iMac 2011 Up to 32GB
Install memory in an iMac - Apple Support
How (And Why) To Install More RAM In Your iMac
NEMIX RAM 32GB (4x8GB Upgrade) DDR3-1333 PC3-10600 204-Pin SODIMM Memory for Apple MacBook Pro Early/Late 2011, iMac Mid 2010 27 inch 4-Core, iMac Mid 2011 21.5/27” , Mac Mini Mid 2011 at Amazon.com