This paper discusses on different kinetic devices and strategies to ensure concentration uniformity within the catalyst zone. For the differential PFR and thin-zone TAP reactor (TZTR), in which uniformity is achieved by making the active zone thin, the generated nonuniformity was quantified and related to the type of transport. It was shown for the TZTR that diffusion mixes up the nonuniformity created by reaction and allows maintaining small nonuniformity (15-20%) in a wide domain of conversions (up to 80%). Contrary to the TZTR, in the differential PFR, the convectional transport does not mix nonuniformity so that its estimate is equal to the conversion, which limits this reactor to the operation at low conversions (e.g., below 20%). This comparison demonstrates a remarkable role of diffusional transport in achieving concentration uniformity in a kinetic experiment.