Measuring 20" square, the beginner Rocker Board is designed for single plane movements and has a maximum angle of 14 degrees. Intermediate Wobble Board features adjustable tilt angles of 10, 12 and 15 degrees and a 360 degree range. Advanced Wobble Board, features adjustable tilt angles of 15, 17, and 20 degrees and has a 360 degree range. Five-inch polyurethane hemisphere spins off easily to accommodate 3/4" spacer that varies the tilt angles of Wobble Boards. Latex free.