Used on helicopter,utility-tactical transport,uh-1 and eh-1 (bell). 3a all ends thread class 12 1st end thread quantity per inch anodize surface treated un 1st end thread series
2a 1st end thread class 14 1st end thread quantity per inch 0.8145 in.min, 0.8166 in. max.pitch dia of thd first end anodize surface treated unf 2nd end thread series
3a all ends thread class 18 1st end thread quantity per inch annular serrations on both sides of hex anodize surface treated uns all ends thread series