We supplied these custom 12 point flange bolts to our automotive customer at 5,000 pieces per size, with size ranging from 12.6MM shoulder diameter X 1.70″ to 12.6MM shoulder diameter X 3.2″. 4140 alloy steel material was used for the production with heat treatment to reach 39-45HRC hardness. Black oxide finish was the last step in the production process. 3/8-16 internal thread was tapped on all size configurations to reach a minimum of 18MM in full thread depth.