Handmade borosilicate glass in the amazing shape of a Reuleaux triangle. A Reuleaux triangle is a shape formed from the intersection of three circles each having its center on the boundary of the other two. Its boundary is a curve of constant width, the simplest and best known such curve other than the circle itself.Constant width means that the separation of every two parallel supporting lines is the same, independent of their orientation. Because all its diameters are the same. It is also the crystalline shape of tourmaline crystals. This could be the perfect glass! 8 oz. 3" x 3" x 3.5" Set includes the six colors in photo.