  We construct a 5D SUSY SU(6) GUT on an $S^{(1)}/Z_2\tm Z_2'$ orbifold. The
first stage of gauge symmetry breaking occurs through compactification and a
specific selection of boundary conditions. Additional symmetries play a crucial
role for the generation of $\mu $ and $B\mu $ terms of appropriate values: with
a $SU(2)_{cus}$ custodial symmetry the Higgs doublets naturally emerge as
massless pseudo-Goldstone bosons in the unbroken SUSY limit. After SUSY
breaking they get masses of the order of the weak scale. If instead of
$SU(2)_{cus}$ a discrete $Z_5$ symmetry is applied the Higgs doublet's masses
are still adequately suppressed, but they are not pseudo-Goldstones. The $Z_5$
discrete symmetry also can be very important for GUT scale generation and an
all order hierarchy. Fermion masses are naturally generated and nicely blend
with additional symmetries. In the considered scenario unification of the three
gauge couplings occurs near $10^{16}$ GeV.
