One of the smoothest rolling reactives I have tried lately is the Lane1 THS Retro Teal Buzzsaw, it easily handles mediums and if you knock the polish off with say 2000grit(us) or 4000grit ab. it is even smoother. I am not really sure if it could handle heavy oil or not because I have other balls for that, and have not tried it, maybe I will just for grins, I am not the heaviest handed in the world either so keep that in mind if considering this ball.
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Patrick