Mallory 1331-L Universal Flatted Shaft Volume Control,; 3-sections selector switches with each section has 12 connectors; outer shaft diameter measures 1/4 inch round shaft (halfway), inner diameter 3/8 inches shaft flat, volume control (broad) base measures 2 3/4 inches full diameter by 2 1/2 inches shaft length; overall length measures 5 1/2 inches long.