An experimental study has been conducted to understand the effectiveness of passive device over base pressure region by modifying the cavity lip radius of an axisymmetric afterbody. The study has been done at both subsonic and supersonic Mach numbers. The effectiveness of the base cavity lip geometry modifications is studied using unsteady base pressure measurements over the base region of the axisymmetric afterbody. Results show that the variation of the time-Averaged pressure is approximately constant in the radial direction for both blunt base and rounded off base configurations at all Mach numbers. The normalized rms pressure fluctuation is approximately constant in the radial direction for both cases. © 2019 Author(s).