SUPERDUO BEADS 2.5 X 5MM Super Duo Beads are a Czech made, glass Two Hole Seed bead. Similar in shape to the Twin bead, but with a few very important differences. Super Duos are a pressed glass bead with guaranteed size and dimensional stability. They measure 2.5x5mm, with two .8mm holes . They are not simply "coated crystal" but actual colored glass with many coating options: Transparent, Opaque, Matte, Color Lined, Picasso, Luster, AB Coating & Magic Line.