This PC-2700 DDR RAM card is compatible with all 12-inch, 15-inch and 17-inch G4 Aluminum PowerBook models except the G4 Aluminum 1.67GHz Hi-Resolution 15-inch & 17-inch models, which use PC2-4200 DDR2 RAM cards. To ensure compatibility, check the RAM already installed in your PowerBook G4 Aluminum by reviewing the detailed memory information found under "About this Mac." The memory should be PC2700 DDR.