Potomac Crystal Cushion 18mm - Siam. A rounded, square shape crystal with a foiled back to enhance and reflect the light. Like Rivoli, these have no holes or settings and are designed to be bezeled with wire or seed beads to create gorgeous projects. This brilliant cushion crystal square stone shape will work with any designs calling for Swarovski 4470 shape. It measures 18mm and comes in a pack of 2. You will love the way it adds sparkle and style to your designs.