The main idea behind the little Higgs models is that the one-loop contribution to the tachyonic Higgs boson mass coming from the top quark cancels. The simplified reason for that cancellation is that a loop's contribution is proportional to the coupling constant of one of the SU (2) groups. Because of the symmetries in the theory, the contributions cancel until there is a two-loop contribution involving both groups. This restricts the Higgs boson mass for about one order of magnitude, which is good enough to evade many of the precision electroweak constraints.