  We comment on a recently discussed possibility of oscillations between
neutrons and degenerate mirror neutrons in the context of mirror models for
particles and forces. It has been noted by Bento and Berezhiani that if these
oscillations occurred at a rate of $\tau^{-1}_{NN'}\sim sec^{-1}$, it would
help explain putative super GKZ cosmic ray events provided the temperature of
the mirror radiation is $\sim 0.3-0.4$ times that of familiar cosmic microwave
background radiation. We discuss how such oscillation time scales can be
realized in mirror models and find that the simplest nonsupersymmetric model
for this idea requires the existence of a low mass (30-3000 GeV) color triplet
scalar or vector boson. A supersymmetric model, where this constraint can be
avoided is severely constrained by the requirement of maintaining a cooler
mirror sector. We also find that the reheat temperature after inflation in
generic models that give fast $n-n'$ oscillation be less than about 300 GeV in
order to maintain the required relative coolness of the mirror sector.
