0fillister head, 0.250 in. H, 0.530 in. Dia, 0.530 in. Dia, 0.156 in. Lg 1st step, 0.374 in. Dia, 0.093 in. Lg 2nd step, 7 worm thds 0.500 in. Diameter 3rd step, 0.563 in. Lg, 0.374 in. Dia, 0.500 in. Lg 4th step, no. 3/8 32 thd on 4th step end, 0.281 in. Lg