Upgrading RAM in the Alienware X51 R3

Hello!

I would like to upgrade my RAM to 16GB but I am not sure what RAM is compatible.

I currently have 8GB Dual Channel DDR4 2133MHz (4GBx2).

When shopping for RAM, is there a specific type I should look out for? I Know DDR4, but anything more than that? Is there RAM the X51 motherboard cannot support?

Thank you for your assistance,

Kintaro