<p>The Knobless Cylinders are the final stage (application) in the dimensional material where the child place order the sets of cylinders based upon his abilities to discriminate. The cylinders have interrelationships in size that are revealed to the child as he works with the set in combination. The Knobless Cylinders set consists of 4 boxes, each contained in a separate wood box with the lid painted the same color as the cylinders. (For age 3-6)</p>