An n-agonal bifrustum is a polyhedron composed of three parallel planes of n-agons, with the middle plane largest and usually the top and bottom congruent.

Set of bifrusta

Example hexagonal bifrustum
Faces2 n-gons, 2n trapezoids
Symmetry groupDnh, [n,2], (*n22)
Dual polyhedronElongated bipyramids

It can be constructed as two congruent frusta combined across a plane of symmetry, and also as a bipyramid with the two polar vertices truncated.

They are duals to the family of elongated bipyramids.


Three bifrustums are duals to three Johnson solids, J14-16. In general, a n-agonal bifrustum has 2n trapezoids, 2 n-agons, and is dual to the elongated dipyramids.

Triangular bifrustum Square bifrustum Pentagonal bifrustum
6 trapezoids, 2 triangles. Dual to elongated triangular bipyramid, J14 8 trapezoids, 2 squares. Dual to elongated square bipyramid, J15 10 trapezoids, 2 pentagons. Dual to elongated pentagonal bipyramid, J16
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