They made it out of ABS, to make is as strong as possible. They plan to make a full set but for now just 1 was made. They used an inner tube as also "stress tested" until it popped. It is an interesting series of videos. The printed wheel starts with this video, but it is slow to watch. He really doesn't get into it until about 2/3 through. The videos following this one are better to watch...
