  In this paper we propose a duality for non-holomorphic N=1 CS-matter theories
living on M2 branes probing Spin(7) cones. We call this duality Spin(7)
duality. Two theories are named Spin(7) dual if they have the same moduli
space: a real Spin(7) cone with base a weak G_2 manifold, and they are hence
holographic dual to the same AdS_4 x G_2 M theory solution. We provide a
systematic way to generate these dualities, derived by combining toric duality
for N=2 CS-matter theories and generalized non-holomorphic orientifold
projections to N=1. Brane construction, AdS/CFT correspondence, and the
computation of the moduli space support our proposal at the classical level and
provide some arguments at the quantum strong coupling regime. The relation with
Seiberg-like duality is also analyzed.
