This is a math manipulative to examine the elliptical cutout which occurs at the intersection of a cylinder with a slanted plane. Planes included are 30 deg, 45 deg. and 60 deg. This is intended to be used in conjunction with the conic sections model to further the understanding of the shapes defined: http://www.thingiverse.com/thing:182820 This concept is of particular interest when you are cutting a hole in your roof for your chimney pipe