Comparison : Item # URD6C, Round Special with Hole and Countersink, diameter 0.389 / 0.395 in
Item # URD8C, Round Special with Hole and Countersink, diameter 0.514 / 0.520 in
Item # #ES-9080, Round Special with Hole and Countersink, diameter 0.323 / 0.329 in