Shape 0 Polymer Ribs are the smallest Polymer Ribs. The traditional kidney-shape of these potters ribs is the most universally recognized clay tool. These little ribs can get into tight places and are good for detail work. All Mudtools polymer pottery ribs are made of a unique flexible material that will not develop burrs or cracks under normal use. Each polymer shape is available in a variety of hardness. See Product Description Tab below for more information. Whether you are throwing clay on the wheel, hand building or sculpting, the pottery rib is a classic and essential tool. With that in mind, there are 9 different polymer ribs and 10 stainless steel ribs available.