A piston rod and piston head are the driven components within a pump. An upstream end of the piston rod is attached within an aperture of the piston head. At least one flute extends between the upstream end of the piston rod and the aperture, and the at least one flute is configured to provide a flowpath for a fluid, such as paint, to flow downstream of the piston head and piston rod. The flutes facilitate a smooth downstream flow of the fluid, thereby reducing hydraulic resistance and reducing wear caused by the fluid.