For discs, the distance between two opposite points on the edge of the object. By definition, a line drawn between these two points will pass through the center of the object.
Controlled Vocabulary
Videodisc. 8 cm.; 12 cm.; 25 cm.; 30 cm.; Other
Analog disc. 5.5 inches; 7 inches; 8 inches; 10 inches; 12 inches; 16 inches; 20 inches; Other
Optical disc. 12 cm. (5-1/4 inches); Other
Cylinder. 2-1/4 inches; 5 inches