Potomac Crystal Cushion 12mm - Black Diamond. A rounded, square shape crystal. 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 12mm and comes in a pack of 2. You will love the way it adds sparkle and style to your designs.