Memory RAM Upgrade for Apple iMac 21.5-inch Mid 2011 4GB/8GB DDR3 SODIMM | eBay
How to Upgrade Memory in a 21.5-inch or 27-inch iMac (Mid 2010) - YouTube
How to install ram in an apple 27" imac (mid 2011) - B+C Guides
How to upgrade RAM / Memory on a 2010 iMac Core i3 i5 i7 (21.5in & 27in) - YouTube
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
New 16GB 4x4GB Memory Apple iMac (21.5 and 27-inch, Mid 2011) PC3-10600 at Amazon.com
Samsung ram Memory Upgrade DDR3 PC3 12800, 1600MHz, 204 PIN, SODIMM for 2012 Apple MacBook Pro's, 2012 iMac's, and 2011/2012 Mac Mini's (16GB kit (2 x 8GB)) at Amazon.com
Memory Upgrades for Apple iMac 2011 Up to 32GB
How to upgrade RAM on iMac 21.5" 2011 - YouTube
iMac 21.5" Mid 2011 How To Change/Upgrade Your Ram For Better Performance 2014 - YouTube
A-Tech 16GB (4x4GB) RAM for Apple iMac (Mid 2010, Mid 2011, Late 2011) | DDR3 1333MHz PC3-10600 204-Pin SODIMM Memory Upgrade Kit at Amazon.com