That is the Paradox! The sand flows from bottom to top – and that somehow makes the time different? While they may not cause time to flow backwards, they are a paradox. | Marked in 3-4, 4-7 & 7-10 minute increments | Measures: 2 7/8" x 2 1/4" x 1 1/8" | Available your choice of the following colors: Light Blue, Light Green, Light Purple, Light Orange or Light Pink | Handmade in Germany