Genuine Apple OEM Video Card for the Early 2009 24" iMac with discrete GPU.  It may be used in as an upgrade to both the NVIDIA GeForce GT 120 or GT130.  

Please note that the 2.66GHz model with the Nvidia 9400M, model MB418LL/A is not compatible with this part.

Compatibility

Apple iMac 24 Inch Early 2009

Identifiers: iMac 9,1 - A1225 - 2267

Model Numbers

MB419LL/A

MB420LL/A

Specs

ATI Radeon HD 4850 graphics processor

• 512MB of dedicated GDDR3 memory
• Mini DisplayPort output port with support for DVI, VGA, and dual-link DVI via adapter
• Built-in iSight camera
• Support for extended desktop and video mirroring modes
• Simultaneously supports full native resolution on the built-in display and up to a 30-inch display (2560 by 1600 pixels) on an external display