The 30' can be used for wider two leg stances with either an extra inflated DynaDisc or the DynaDisc Plus . It can also be used in a sitting position thereby increasing the demand in stabilizing and coordinating the center of the body. In a seated position you can rotate the board along its edge both clockwise and counter clockwise and rock the board symmetrically to the left and right, forward and backwards, and on diagonals. The DynaBoards are made of 12' to 58' high quality Baltic Birch and coated with an aluminum oxidesand non skid surface.