The Cylinder Blocks (also called the Knobbed Cylinders) are a classic piece of Montessori material that helps to develop a child's skills in size differentiation, sorting, and hand/eye coordination. Block #1 features ten cylinders, where the diameter of each piece increases with the height (i.e. from short and narrow to tall and wide). Each block and cylinder is made of solid beechwood with a natural, satin finish. The block measures 46 cm (about 18") long.