OK, Looking to build a WW ll sub and I guess it would be sub launched under water torpedo. US or Japanese sub. the scale I don’t know yet but the kit would be no longer then 12".
USN sub launced torpedoes were normally 21" in diameter and 20.5’ long. IJN sub launched torpedoes were 21" diameter and 23.5’ long. Here’s a link to some info on USN torpedoes.
White Ensign makes some 1:144 scale USN 21" torpedoes.