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
32GB (4 x 8GB) PC10600 DDR3 1333MHz SO-DIMMs Memory Compatible with 2011 MacBook Pro, Mid 2010/2011 21.5" & 27" iMac Models, 2011 Mac Mini (OWC1333DDR3S32S) at Amazon.com
Install memory in an iMac - Apple Support
32.0GB OWC Memory Upgrade Kit For 2010-2011 Apple iMac
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
16GB -2x8GB Memory Ram Upgrade for 27" Apple iMac-12.2 Core i5 2.7GHz Mid 2011 | eBay
Timetec 32GB KIT(4x8GB) Compatible for Apple DDR3L 1600MHz PC3L-12800 CL11 for iMac (Mid 2011, Late 2012, Late 2013, Late 2014 Retina 5K, Mid 2015 Retina 5K) SODIMM Memory Module MAC RAM Upgrade at Amazon.com
Install memory in an iMac - Apple Support
Install memory in an iMac - Apple Support
Memory Upgrades for Apple iMac 2011 Up to 32GB
How to Upgrade Memory in a 21.5-inch or 27-inch iMac (Mid 2010) - YouTube
How-To: Boost your Mac's speed and prolong its useful life with easy RAM upgrades - 9to5Mac