Final answer:
A compass is the tool that allows us to draw perfect circles with a set radius.
Step-by-step explanation:
The tool that allows us to draw perfect circles with a set radius is the compass. A compass consists of two arms, one with a sharp point and the other with a pencil or pen. The sharp point is used to anchor the center of the circle, and the pencil or pen is used to draw the circumference. By adjusting the distance between the two arms, we can set the radius of the circle we want to draw.