Apple iMac 21.5-inch | Extended Warranties & Free Shipping
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
Maxing out memory on iMac (2011) | MacRumors Forums
Maximum memory for 2011 iMac - Ask Different
Install memory in an iMac - Apple Support
Apple iMac 27" All-In-One Desktop - MC814LL/A 2011 for sale online | eBay
Upgrade Options for Apple iMac 27-Inch 2011
How to Upgrade iMac RAM (21.5" and 27" Aluminum): EveryMac.com