OWC 2.0TB HDD Upgrade Kit for All 2011 iMac Models - Amazon.com
Refurbished: Apple Desktop Computer iMac MC978LL/A Intel Core i3 2nd Gen 2100 (3.10 GHz) 4 GB 500 GB HDD AMD Radeon HD 6750M Mac OS X 10.12 Sierra - Newegg.com
Apple iMac i5 21.5" AIO Desktop Computer Core i5 2.5GHz 8GB 500GB Sierra 2011 and WIFI
apple-history.com / iMac (Mid 2011)
Apple iMac (spring 2011) review: Apple iMac (spring 2011) - CNET
Amazon.com: Original Graphics Video Card for Apple iMac 2011 Core i5 2.7 A1312 MC813LL/A MC813 27 Inch Desktop PC Computer AMD Radeon HD 6770M HD6770M GDDR5 512MB 109-C29557-00 Replacement Parts : Electronics
What You Should Know Before You Buy a 2011 iMac
Apple 21.5" iMac All in One Desktop Computer Core i5 4GB Ram 500GB HD OS High Sierra and WIFI Keyboard And Mouse - GRADE B