It's got an aluminum base, but it uses direct touch heat pipe technology so the copper heat pipes directly touch the cpu and that is how it cools so well. And as the picture shows Xigmatek > Tuniq.
Here is what the Xigmatek base is like:
It has like 5-6 rows (can't remember exactly). 3 are the copper heat pipes, and 3 are the base of the cooler. They go every other one so it's aluminum, copper, aluminum, copper, etc.