Picket Fence Studios Speed of Light Gem Mix are high-quality flat-back gemstones. Comes in compact cases with clear lids - ready to store and use as soon as they arrive, and they even let you peek in from the side to grab the mix you want easily from a stack. The lids are flat, so the containers can be stacked on a shelf or in a drawer. Each compact is a mixture of 3 colors and 4 different sizes ranging between 2-4mm. Stone weight 12-13 grams. Approximately 750 stones in each compact. The flat gem, sparkly gems are in vibrant blues, pinks and iridescent colors.