The roller has a different form in different models. Some are a cylinder and some are a cylinder in their midsection that tapers toward the two ends. That tapering enables tricky moves by the rider. Four of the models produced by Vew-Do Balance Boards each have a roller whose shape has a different taper, designed for doing different tricks and simulating different boardsports. (One of those four is the roller at the top of the photograph to the side of this paragraph.) Vew-Do's patent gives information about the effect that its roller's shape has on the board's movement.