This Pro Bead Roller will roll two bead sizes, both ovals. One is 19 x 7 mm, the other is 18 x 9 mm. The beads rolled with this set can be pierced while they are inside the bead roller, avoiding the possibility of fingerprints or distortion from handling the bead to pierce it. About 20 bead piercing pins are supplied with this Pro Bead Roller. See the 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. Your satisfaction is guaranteed with all of our products!