What are they? I see the "1867 MHz DDR3 SDRAM" part. But what about the rest? This post had some information: http://forums.macrumors.com/threads/ram-question.1928280/ But more specifically, I want to know what Apples sends you with a new machine, and what do I need to look for when trying to find compatible RAM? Which of things like registered/unbuffered, pin #, speed, CL, etc matter? Here are some of the suggestions for things to buy, and I've been using the listed specs to try and piece it together: 1) http://eshop.macsales.com/item/Other World Computing/1867DDR3S32S/ 2) Crucial Ballistix Sport 16GB Kit (8GBx2) DDR3 1866 (PC3-14900) 204-Pin SODIMM Memory BLS2K8G3N18AES4 / BLS2C8G3N18AES4 EDIT: Based on the pictures here, it looks like This is the RAM that Apple Ships. You can download the technical specs .pdf to get ~all of the information you could want. I'd still be curious to know more about compatibility.