Many basic shapes do not have an unambiguous length. However, cylinders are kinds of line segments with an additional radius or thickness, and since line segments have a rather unambiguous length, it would make sense to add a method Base.length(::GeometryBasics.Cylinder), defined as the norm of the vector LinearAlgebra.norm(c.extermity - c.origin) for a c::GeometryBasics.Cylinder.