The OWC 1600MHZ DDR3 204-Pin SODIMM PC3-12800 RAM is designed specifically for the Retina 5K 27'' Late 2015 iMac, offering a total capacity of 16GB in two 8GB modules. With a bus speed of PC3-16000 (DDR3-2000), this RAM provides fast and efficient performance for your computer. The OWC brand ensures reliability and quality, making it an ideal choice for upgrading your memory capacity and enhancing the performance of your iMac.