Original Ati HD 6970M 5750m 4850 4670 Graphics Card Video Card 1GB 2GB 109-C29657-10 For Apple iMac 27" A1312 GPU 2009 2010 2011 - AliExpress
For iMac A1311 21.5" Mid 2011 AMD Radeon HD 6750M 512MB Upgrade Nvidia K1100m 2GB GDDR5 Video Graphics Card MC309LL/A MC812LL/A - AliExpress
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Amazon.com: Valley Of The Sun Original Graphics Video Card GPU Replacement for Apple iMac A1311 Mid-2011 Core i5 2.7 MC812LL/A MC812 21.5 Inch Desktop Computer, AMD Radeon HD 6770M GDDR5 512MB Repair