This is a 20mm (4/5 inch) cube so it's small. Be careful with this size: not for small children, danger of suffocation. But I really like the little things. I'm not sure if this is a really nice adult toy, a possible combination of color filter and mirror, or a color learning tool. First, it works as a combination prism in direct sunlight (not very well in low-intensity lighting). The color combinations are incredibly vibrant. I sat on the floor and turned the cube in the sun to see the colored patterns on the wall. I then tried lifting it up to look through the cube at the color filters/mirrors. This is funny! On a more practical side, it's not a camera filter or mirror. There are many that work better. So I'm not sure if this is a practical tool but more of a fun toy for adults or an educational tool. But this is NOT a toy for children.