Ring hinge

This ring hinge can only be produced by 3D printing. There are two types of this hinge. One of them lets to turn around as many times as you want. The other has the stops within the ring. This way you can only open the hinge until a given angle. A small plus in the design that if you need more hinge built in one, than you can apply as many hinges as you want. I will upload later some examples of use.