iMac Intel 27" EMC 2374, AMD Radeon HD 4850 Video Card Removal & Repair - iFixit Repair Guide
iMac 2009 to 2011 (A1311/A1312) Upgrade Guide – MacintoshMen
iMac Intel 27" EMC 2374, AMD Radeon HD 4850 Video Card Removal & Repair - iFixit Repair Guide
Amazon.com: Original Graphics Video Card GPU Upgrade Replacement for Apple iMac 21.5 Inch Late 2011 Core i3 3.1 All-in-One Desktop PC MC978LL/A, AMD ATI Mobility Radeon HD 6750M, MXM VGA Board Repair
Intel iMac 27" AMD Radeon 6970M 1GB Video Card, Mid 2011 DIY Parts replacement Video Cards
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
Amazon.com: Original Graphics Video Card GPU Upgrade Replacement for Apple iMac 21.5 Inch Late 2011 Core i3 3.1 All-in-One Desktop PC MC978LL/A, AMD ATI Mobility Radeon HD 6750M, MXM VGA Board Repair
For iMac 21.5" A1311 Mid/Late 2011 AMD upgrade Nvidia K2100m 2GB Video Card | eBay