Abstract: A massage device comprising a ball and a base with a single channel defined by a rim. The single channel contains a middle surface that has a concave arc shape along its length and a constant arc depth. The ball has a ball radius that is substantially equal to the constant arc depth. The ball is capable of being freely inserted into and freely removed from the single channel. When the ball surface makes contact with middle surface, the ball may roll in a longitudinal direction, while the concave arc shape limits the ball from rolling in a lateral direction.