Microchannel systems for multilamination mixers can be obtained by stacking and bonding microstructured foils. So-called V-type mixers have been manufactured and examined at the Institute for Micro Process Engineering by means of the Iodide Iodate Reaction Method. In previous work we showed that V-type mixers can be scaled by varying the number of micromachined foils and holding constant velocities of the fluids exiting the microchannel system. Applying the Iodide Iodate Reaction Method, constant triiodide concentrations, indicating constant 'mixing qualities', were obtained with mixer inlays with 6 foils, 12 foils, and 24 foils. In order to understand the influence of the top- and the bottom foils, which are different regarding their geometrical environment, examinations are presented with mixer inlays with 4 foils and 2 foils. The two newly examined inlays are fully 'in-line' with the scaling considerations from the previously examined devices. An influence of the boundary foils cannot be shown. Furthermore, it is shown that the arrangement of the microchannels at the interface between the microchannel system and the mixing chamber ('shape of the exit window') has a crucial impact on the mixing results: the larger the width of the exit window, the better the mixing results. (C) 2010 Elsevier B.V. All rights reserved.