Supersymmetric unified models in which the Z couples to the Higgs doublets, as in the E 6 class of models, have large fine tuning dominated by the experimental mass limit on the Z . To illustrate this we investigate the degree of fine tuning throughout the parameter space of the Constrained Exceptional Supersymmetric Standard Model (cE 6 SSM) that is consistent with a Higgs mass m h ∼ 125 GeV. Fixing tan β = 10, and taking specific values of the mass of the Z boson, with M Z ∼ 2 − 4 TeV. We find that the minimum fine tuning is set predominantly from the mass of Z and varies from ∼ 200−400 as we vary M Z from ∼ 2−4 TeV. However, this is significantly lower than the fine tuning in the Constrained Minimal Supersymmetric Standard Model (cMSSM), of O(1000), arising from the large stop masses required to achieve the Higgs mass.