Stand, sit, or kneel! The Rocker Board moves in one directional plane and has a large square design for beginners. The Wobble Boards move in multiple planes and have a smaller round design for intermediate and advanced users. Both Wobble Boards offer 3 levels of difficulty and adjust in seconds with a turn of the patented sphere on the bottom of the board. As balance improves, simply turn the sphere to a steeper angle for a greater challenge. All 3 boards feature birch wood construction with slip-resistant top. 20" Wobble Board: 10°, 12°, or 15° angle. 16" Wobble Board: 15°, 17°, or 20° angle.