Aurora R5, looking to add extra video card. What is compatible?

Hi,

I'm looking to add an extra video card to my Aurora R5. Currently has the GeForce GTX 1070 8GB DDR5. I understand it has SLI capabilities? Aside from another GTX 1070, what other Nvidia video cards can I pair it with for it to work? Was thinking if it's possible to link with the 16 series. Help appreciated.

-Kevin