HOW TO: Upgrade The RAM to 32GB on a Mid-2011 21.5inch iMac - YouTube
21.5” mid-2011 iMac wires? Finally trying to upgrade my RAM and these wires are blocking the slot — did get an iMac with poor build quality? What can I do? : r/mac
How to Upgrade iMac RAM (21.5" and 27" Aluminum): EveryMac.com
Install memory in an iMac - Apple Support
NEMIX RAM 32GB (4x8GB 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
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