8x5mm Backlit Uranium GemDuo 2-Hole Czech Beads Tube. The GemDuo is a 2-hole 8x5mm diamond shaped Czech glass bead. This diamond shaped bead is domed so it will add beautiful depth to your designs. The 2 parallel holes will be perfect for bead weaving and multi-strand projects. These beads are very similar to DiamonDuos so they can be used interchangeably. These beads come conveniently packed in 2.5" tubes. Approximately 8 grams per tube. There are approximately 62 beads per tube.