Sherrill Mudtools Polymer Rib for Pottery and Clay Artists, Small Bowl Rib, Blue Firm Potters Ribs are essential tools for throwing clay on the wheel, hand building or sculpting. Small Bowl Ribs are designed to give as many radius sweeps on the clay as possible. They are made with a stiff polymer but still offer some flexibility. Color of rib dictates level of firmness. 5 inches x 2 inches . Made in USA!