Slant Board increases extension in the lower and upper back while stretching the calves. Board is made of a heavy-duty composite plastic. Angle of incline adjusts to 4 levels and folds flat (3-inches) to store easily. Levels are 0, 5, 15, 25, and 35 degrees. The last slot on the board makes an excellent hand-hold for stretching. Non-slip top measures 14" x 14".