The work presented here, however, suggests that there is no difference for BOPP compared to PET, as for each BOPP film type, the plain and AlOx coated films showed similar/identical surface roughness. Nevertheless, the authors still assume that the AlOx layer grows in a differentmanner on BOPP than it does on PET, due to the different surface chemistry, and this contributes to the different barrier properties. This nanostructure of the coating does, however not affect the roughness of the AlOx coating, asmeasured by AFM, i.e. it is beyond the resolution of this analytical technique at the chosen scan size.