We present first direct results of SANS measurements of the form factor of matrix chains in a cross-linked, silica filled elastomer in the isotropic state. The structure of the secondary filler network of silica is investigated in parallel in the unlabeled analog at identical filling degrees. Limits of the scattering description of these 2-phase/3-components mixture are tested. This investigation is a pilot study in the understanding of the reinforcement process by silica in the deformed state.