The bottom of a pyramid is a square, but when the bottom is a triangle, the object is called a tetrahedron, or a triangular pyramid. Still, tetra shaped pouches are often called pyramids. Despite the confusion and hair splitting, tetra pouches look funny and interesting. Who cases whether they are practical or not? I would recommend tetrahedron cosmetics bags especially for travelling people. A tetra makeup pouch placed in a bathroom of a three star hotel immediately raises the standard of your room and makes you feel pampered! You will find these pouches in my Etsy shop.