Cobalt Blue AB 4mm Round Czech Fire Polish Glass Beads Czech Fire Polished Beads In color "Cobalt AB," a clear glass with AB finish. The AB finish is a rainbow effect applied to 50% of the surface of each bead, for beautiful reflections throughout. Measurements: 4MM long, 3.5MM wide. In Czech Fire Polished beads, the shape called "Round" is actually more of an oval. Quantity: 50 beads, which is approximately 8 inches of beads when strung.