4.0GB OWC Memory Upgrade For 27" & 21.5" iMac (Mid & Late 2011) - ynzal.com
OWC Hard Drive Upgrade Kit for Apple iMac 2011
iMac RAM upgrade: Here's an affordable way to improve multitasking - CNET
How-To: Boost your Mac's speed and prolong its useful life with easy RAM upgrades - 9to5Mac
OWC 8GB (2 x 4GB) PC12800 DDR3L 1600MHz SO-DIMMs Memory Compatible with 2011-2015 iMac, 2011-12 Mac Mini, and 2011-2012 MacBook Pro (Non-Retina Display) Models (OWC1600DDR3S08S)
OWC 1866D3R9M64 64.0GB 4 x 16.0GB PC3-14900 DDR3 Mac Pro Late 2013 RAM Memory Matched Set - 4 x 16GB
OWC 8GB (2 x 4GB) PC12800 DDR3L 1600MHz SO-DIMMs Memory Compatible with 2011-2015 iMac,
OWC HDD Compatibility For all Apple 2009-2010 iMac 21.5" and 27" Models With SMC Compatibility Model OWCDIDIMACHDD09 - Newegg.com
32.0GB OWC Memory Upgrade Kit For 2010-2011 Apple iMac