The difference between the two models is mainly the diameter but the feel is relatively the same. The Optimo Pro are thicker and heavier than Optimo One. The Optimo One measures at 1.6 inches thick and are meant to fit most hands for men and women. The Optimo Pro are 2.25" inches thick and will probably not fit small hands. The Optimo Pro grips challenges your grip and forearm and whole upper body through muscle irradiation. The weight has to be moderated due to the increased size of diameter. The Optimo One are great functional strength training and light to heavy weight.