The aspect ratio of nanoparticles governs their percolation threshold in polymer composites, and thus exerts a significant influence on the materials properties. We explored how the combination of two rodlike particle types with different aspect ratio, but otherwise similar characteristics, affects the properties of nanocomposites. Using experimental data of composites made with two different cellulose nano crystal (CNC) types, we show that a substantial fraction of the high-aspect-ratio CNCs can be substituted with the low-aspect-ratio nanoparticles without significantly affecting the properties. Exploring the boundary limits of aspect ratios, where random contact criterions and mean field approximations are valid, we formulated a generalized theoretical model that permits predicting the modulus of nano composites with two rod-like nanoparticle types having different length distributions. The model shows that the modulus of such nanocomposites is strongly weighted by the particles with higher aspect ratio. (C) 2016 Elsevier Ltd. All rights reserved.