Timetec 16GB KIT(2x8GB) Compatible for Apple DDR3L 1600MHz for Mac Book Pro(Early/Late 2011,Mid 2012), iMac(Mid 2011,Late 2012,Early/Late 2013,Late 2014,Mid 2015), Mac Mini(Mid 2011,Late 2012) MAC RAM at Amazon.com
32.0GB OWC Memory Upgrade Kit For 2010-2011 Apple iMac
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
Install memory in an iMac - Apple Support
Memory RAM Upgrade for Apple iMac 21.5-inch Mid 2011 4GB/8GB DDR3 SODIMM | eBay
iMac RAM Models 11.3 (i5 and i7 only) to 12.2 (8GBx4) | MacMemory.com
iMac RAM for Model 11.2 to 12.2 | DDR3-1066MHz | 8GB | MacMemory.com
Memory Upgrades for Apple iMac 2011 Up to 32GB
Install memory in an iMac - Apple Support
How to Upgrade the RAM in Your iMac
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
16GB -2x8GB Memory Ram Upgrade for 27" Apple iMac-12.2 Core i5 2.7GHz Mid 2011 | eBay