Timetec Hynix IC 8GB KIT(2x4GB) Compatible for Apple DDR3 1067MHz / 1066MHz PC3-8500 for MacBook, MacBook Pro, iMac, Mac Mini (Late 2008, Early/Mid/Late 2009, Mid 2010) MAC SODIMM Memory RAM Upgrade
Install memory in an iMac - Apple Support
Is it worth it to upgrade RAM on Mid 2010 21.5 iMac? | MacRumors Forums