Guild Wars 2

When I try to craft them together it says there is an unknown recipe but I cant figure out what else needs to go in there? Anyone have any ideas as to what it might be?

you need to use the armor craft “Armorsmith, Leatherwork, tailoring” you put the 2 + the orichalcum helmet lining/casing in the discovery mode. (I’m not sure about the name for tailoring and leatherwork, but it’s the peices you need to craft lvl 80 exotic helmet)

The 2 helmet crafting components of the weight class you want your mantle to be.
Or so I’ve heard.

AH DUH ok thank you very much