These special rollers look oblong--but if you place a book over the top of them, they roll evenly like a ball was underneath. What is happening here? If you have a rotary engine in your car, you may already be familiar with how it works.

Based on a mathematics, these shapes are called solids of constant width, more specifically the Meissner-Schilling modification of the Reuleaux tetrahedron.

Each order will give you three individual rollers. Products shown in White Oak.