Material steel qq-s-636 hr p^o 0.0598 in. Thk, finalfinish prime mil-p-13380, consists of one ea side bow, inner p/n 7370417 fscm 19207, one ea p/n side bow, outerp/n 7370418 fscm 19207, one ea spacer p/n 7064364 fscm19207, 21.000 in. O/a lg, 1.000 in. O/a thk