Shape 4 Polymer Rib Blue FirmShape 4 Polymer Rib Blue Firm Sometimes you need to make a point! The corner on Shape 4 gives a beautiful line on the clay. You also get two flat surfaces and three radiuses. Michael wants this one in his toolbox if hes stranded on a deserted island. All of our polymer ribs are made of unique flexible materials that are resistant to cracking and the formation of burrs. We've found that with general use these ribs become burnished over time. Each