It is comprised of 2 plastic components: a center shaft and the remaining frame of the pogo stick. There is also a spring and pin to allow the pogo stick to have a fully functioning range of motion.
The pogo stick was a fun idea I had while I was working for a company that had a 3D printer. It was the first thing I ever designed that wasn't work-related. Although it is simplistic in nature, the concept behind designing the pogo stick is challenging in regards to range of motion and the ability to be assembled, but not taken apart.
I really love working with ProE and similar CAD programs and the ability to create your designs into a 3D model is fascinating to me. I love it and hope that I can create more designs!