Amazon.com: GDDR5 2GB Graphics Video Card Radeon HD 6970M for Apple iMac Mid-2011 27 Inch Core i5 i7 All-in-One Desktop PC Computer, AMD Radeon HD6970M HD6970 MXM Board GPU Upgrade Repair Parts :
Used Apple iMac 27-inch 2011 ATI Radeon HD 6970M (2.0GB) Video Card 661-5969 | mac of all trades
661-5969 - Apple AMD Radeon HD 6970M 1GB GDDR5 256-Bit MXM-B 3.0 Video Graphics Card for iMac