Description:
 
Knobless cylinders are a Montessori sensorial material used to help children develop visual discrimination skills: 
What they are
The cylinders come in four boxes, each containing ten colored cylinders. The cylinders are different in height and diameter, and each set of cylinders is a different color: 
Green: The cylinders decrease in diameter but increase in height 
Blue: The cylinders decrease in height but remain the same diameter 
Red: The cylinders decrease in diameter but remain the same height 
Yellow: The cylinders decrease in both diameter and height