3.4992" bore diameter 2.7100" housing length internal raised surface on closed flange 0.785 in. high by 0.625 in. od center tapped on outside surface w/3/8-24 nf class 2 sti thds 0.4500 in. lg., no. 3591-60n x 3/8 insert installed in threaded hole, used on trunnion bearing, main rotor flange block