HOW TO: Upgrade The RAM to 32GB on a Mid-2011 21.5inch iMac - YouTube
Amazon.com: Timetec 16GB KIT(2x8GB) Compatible for Apple DDR3 1333MHz PC3-10600 CL9 for Mac Book Pro (Early/Late 2011 13/15/17 inch), iMac(Mid 2010, Mid/Late 2011 21.5/27 inch), Mac Mini(Mid 2011) MAC RAM Upgrade :
RAM Upgrade for iMac Mid 2011 21.5-inch | MacRumors Forums
iMac 21.5" Mid 2011 How To Change/Upgrade Your Ram For Better Performance 2014 - YouTube
Install memory in an iMac - Apple Support
Install memory in an iMac - Apple Support
NEMIX RAM 16GB (2x8GB 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
iMac RAM upgrade: Here's an affordable way to improve multitasking - CNET
Install memory in an iMac - Apple Support
Install memory in an iMac - Apple Support
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
How to Upgrade iMac RAM (21.5" and 27" Aluminum): EveryMac.com
Amazon.com: Timetec 8GB KIT(2x4GB) Compatible for Apple DDR3 1333MHz PC3-10600 for Mac Book Pro (Early/Late 2011 13/15/17 inch), iMac (Mid 2010, Mid/Late 2011 21.5/27 inch), Mac Mini(Mid 2011) RAM Upgrade : Electronics
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
Install memory in an iMac - Apple Support
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
How To Upgrade RAM in a Mac | Macworld
iMac Mid 2011 (21.5 – inch and 27 – inch) RAM Upgrade Dallas – Apple Mac Computer Repair Dallas , Laptop ,Desktop ,iMac ,MacBook iPhone iPad Data Recovery ,Virus
install - Installing and Upgrading Ram on a mid 2011 iMac (different size RAM) - Ask Different