All of our Mudtools polymer pottery ribs are made of a unique flexible material that will not develop burrs or cracks under normal use. We've found that over time the rib becomes even more polished. Each polymer shape is available in a variety of hardness. Sometimes you need to make a point! The corner point on the Shape 4 Polymer Ribs gives a beautiful line on the clay; you also get two flat surfaces and three radiuses. Michael wants this one in his toolbox if he's stranded on a deserted island. The Red Very Soft is excellent for finishing passes. Whether you are throwing clay on the wheel, hand building or sculpting, the pottery rib is a classic and essential tool. Because it acts as an extension of the potters own hand, we believe it should function well and be a joy to use.