Used on aircraft application. 3a 1st end thread class 2 2nd end bolt hole quantity 16 1st end thread quantity per inch anodize surface treated un 1st end thread series
3 all ends bolt hole quantity 16 1st end thread quantity per inch 1.4454/1.4494 in.pitch dia thd first end anodize inside surface treated uns 1st end thread series
3a 2nd end bulkhead thread class 12 2nd end bulkhead thread quantity per inch anodized light gray anodize surface treated un 2nd end bulkhead thread series