CORSAIR Mac Memory, 8GB 1333MHz C9 DDR3 SODIMM for Apple iMac, MacBook and MacBook Pro 4GB (2x4GB). Tested at Apples compatibility lab to ensure functionality with all current products that have official Apple support for 4GB SO-DIMMs. Adding system memory is one of the most effective ways to improve overall performance and Corsair?s Mac Memory offers a solid tested solution with a limited lifetime warranty. Density: 8GB (2x4GB SO-DIMM) Speed: 1333MHz CL9 Timing: 9-9-9-24 (1333 MHz) Type: DDR3 Format: SO-DIMM Pin Out: 204 Pin Voltage: 1.5V