Four rectangular wooden blocks, into each of which is drilled a row of ten cylindrical wells or sockets, in each of which rests a precisely fitted wooden cylinder with a small spherical knob on top. The cylinders and their corresponding wells vary in diameter and/or height from 5.5 centimeters to 1.0 centimeters, in increments of 0.5 centimeters. Our Knobbed Cylinders are free from defects and poor craftsmenship. Made from Rubberwood (hardwood) in Thailand. Block 1 cylinders are all 5.5 cm tall, and decrease in diameter from 5.5 cm to 1 cm. Block 2 cylinders decrease in both diameter and height from 5.5 cm to 1 cm for both. Block 3 cylinders decrease in diameter while increasing in height, ranging from 1 cm tall and 5.5 cm in diameter to 5.5 cm tall and 1.0 cm in diameter. Block 4 cylinders are all the same diameter (2.5 cm), and decrease in height from 5.5 cm to 1 cm.