Shape 3 Polymer Rib Yellow SoftShape 3 Polymer Rib Yellow Soft Shape 3 is 5" wide and gives a good sweep across the clay. This is a good rib if you throw larger objects. Michael Sherrill uses the Green Medium or Blue Firm because they are stiffer and bite into the clay. 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 polymer rib