Sci-fi Helmet - Hard Surface Exercise

Here's the model I made for the Zbrush Exam for the Concept Art course I'm attending. We studied Hard Surface Sculpting along with the Zmodeler brush and had to make a sci-fi themed helmet. As a based we used the same head we did for the face sculpting exercise which you can find on my profile.
The model is not perfect since we study only the basics of 3D.