Enhance the performance of your iMac 27" late 2012 or MacBook Pro mid 2012 with 4GB Crucial DDR3 SO DIMM memory module. It has 1600MHz memory speed. This dual-rank memory module kit increases your computer's RAM, enabling more applications to run simultaneously without system glitches. The non-ECC unbuffered DDR3 PC3-12800 RAM memory module features a 1600 MHz clock speed, a CAS latency of 11, and a power rating of 1.35/1.5V. To use this module, your system must have both a 204-pin SO-DIMM slot and a DDR3-enabled chip.