Dini Surface

The surface of a ball (a sphere) has the same positive Gauss Curvature in every point. It is very interesting that there are also surfaces with the same negative Gauss Curvature in every point. Some are surfaces of revolution, but there are also some other surfaces with this property (at least away from some singular curves). One of the most classical ones is the Dini surface. We provide the Dini surface in two sizes: medium (about 20cm) and large (about 30cm).