Pro Bead Set 5 rolls a single bi-cone shaped bead with blunt ends. The length of the bead it can roll is 42 mm. The diameter of the center of the bead is 17mm. This bead roller does have a bead piercing pin path through it, so the bead can be pierced through the roller, eliminating the likelihood of fingerprints, and possible distortion. Additionally there is a 1/16 inch rule on the edge of this to assist you with measuring clay according to directions, as well as s a line at the pin path to assist lining the bead up for piercing. A tube of bead piercing pins is provided with this bead roller. See our Pro Bead Rack in the Miscellaneous category. Polymer clay is the clay primarily used here at Poly-Tools, Inc., but other clay mediums can be used successfully with our bead rollers.