DDR3 1066MHz PC3-8500 204-Pin Unbuffered Non ECC 1.5V CL7 Dual Rank 2Rx8 based 256x8 Module Size: 16GB KIT(4x4GB Modules) Compatible for Apple iMac - 21.5 inch / 27 inch Late 2009 - iMac10,1 iMac11,1 Model Number: A1311 A1312 - Part Number(s): MB953LL/A, MC507LL/A, MB950LL/A, MB952LL/A, BTO/CTO Supports CPU Processors: 2.66 GHz Core i5, 2.8 GHz Core i7, 3.06 GHz Core 2 Duo, 3.33 GHz Core 2 Duo Guaranteed Lifetime warranty from Purchase Date and Free technical support based on United States Timetec 16GB KIT(4x4GB) Compatible for Apple DDR3 1067MHz / 1066MHz PC3-8500 CL7 Dual Rank for iMac (Late 2009 21.5-inch / 27-inch) SODIMM Memory MAC RAM Upgrade for iMac 10,1 and 11,1