A device that teaches the relationship between a circle, its diameter and its radius. The device includes a circular ring that has a rigid intersecting bar representing its diameter. Attachment mechanism allows flexible diameter bars to be attached around the outer perimeter of the circle. Flexible bars the same size as the diameter or the radius are available to attach to the outer perimeter by way of the attachment mechanism. Additional flexible bars are available at 0.14 diameters and 0.28 radiuses in length. When the flexible diameter bars are attached to the circle, three diameters bars and one 0.14 diameter bar are affixed around the circle's circumference representing 3.14 diameters. When the flexible radius bars are attached to the circle, six radius bars and one 0.28 radius bar are affixed around the circle's circumference representing 6.28 radius.