Measuring 20" square, the begineer Rocker Board is designed for single plane movements and has a maximum angle of 14 degrees. Intermediate and advanced Wobble Boards are excellent for single or dual-leg standing tilt angles of 10, 12 and 15 degrees and a 360 degree range. Advanced Wobble Board, designed for higher-level users, 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 ¾"spacer that varies the tile angles of Wobble Boards. Top-grade plywood construction with birch-grain finish and non-slip surface. Latex free.