This module has been ordered for the upgrading of an iMac (early 2008). This can take up (2 GB x 2) according to the specifications 4GB. However, there are opinions that this iMac generation can also be upgraded to 2 GB + 4 GB unless you find a 4GB-module with the appropriate specifications. For this, there are very few suppliers, including Komputerbay. The upgrade to 6GB with the module specified here worked perfectly.