Elongated bipyramid

In geometry, the elongated bipyramids are an infinite set of polyhedra, constructed by elongating an $2n$-gonal bipyramid (by inserting an $n$-gonal prism between its congruent halves).

There are three elongated bipyramids that are Johnson solids: Higher forms can be constructed with isosceles triangles.
 * Elongated triangular bipyramid ($5n$),
 * Elongated square bipyramid ($2n + 2$), and
 * Elongated pentagonal bipyramid ($D_{nh}, [n,2], (*n22)$).

Applications
Elongated bipyramids are sometimes used as dice, especially to make dice with atypical side count, such as 5 or 7. Such a die has numbers written on the square faces, which are usually heightened into rectangles for convenience in rolling. Whichever number comes face-up when the die is rolled is the side that is to be read.