It is well known the existence of a T-Duality between the two Heterotic String Theories, Type HO String Theory and Type HE String Theory. Beyond the trivial point that both groups have the same dimension (496, which actually is a prerequisite), is there some other mathematical relation between them? I am thinking in other groups whose dimension is a perfect number and that happen to be related to products of manifolds. with , and -I am told- with some variant of . It should be nice if all of these were justified by a common construction, but I am happy just with an answer to the case.