Potomac Crystal Rivolis - Opal Collection. These high-quality rivolis feature a pointed foiled back to enhance reflection and add dazzling sparkle to your projects. These crystals have no holes and can be incorporated into a variety of bead weaving and wire working techniques to include them in your designs. Be inspired and get creative with this collection of stunning mystic colors. They measure 10mm and come in a pack of 25 (5 of each color).