32.0GB OWC Memory Upgrade Kit For 2010-2011 Apple iMac
Rasalas 8GB Kit (2X4GB) PC3-10600 DDR3 1333 mhz Sodimm RAM Upgrade for AMD Intel Laptop, MacBook Pro 13/15/17 inch Early/Late 2011,iMac 21.5-inch Mid/Late 2011,27-inch Mid 2011,Mac Mini 5,1 & 5,2 Mid at
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
A-Tech 32GB (4x8GB) RAM for Apple iMac (Mid 2010 27 inch 4-Core, Mid 2011 21.5/27 inch) | DDR3 1333MHz PC3-10600 204-Pin SODIMM Memory Upgrade Kit at Amazon.com
Apple iMac Upgrades | SimplyFixIt
Install memory in an iMac - Apple Support
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
Apple iMac Mid 2011 21.5-inch 2.7GHz Core i5 Apple DDR3 RAM Memory | Kingston
Memory RAM Upgrade for Apple iMac 21.5-inch Mid 2011 4GB/8GB DDR3 SODIMM | eBay
Apple 21.5” iMac (Mid 2011); iMac12,1 Installation Guides and Specifications - Macfixit Australia