Reflecting holographic storages with a read-out efficiency of up to 60% are obtained in Mn doped KNSBN crystal by using He-Ne laser beams of uW powers. It is found theoretically and experimentally that high road-out efficiency can be realized with a weak object beam and a stong reference beam in the conditions of our experiments. The ratios of eletrooptical tensor elements of the crystal are estimated within the range of the constant coupling factor.