Unfortunately I'm not very mechanically-inclined myself, so I'm not the right person to ask. Some kind of metal, but anything more specific than that I can't answer for sure. I'm sorry I can't be more helpful.

[He hadn't asked too many questions at the time anyway. It was better than what he had it's place previously, and that was all he cared about.]

And there wasn't any problem with your body rejecting the heart belonging to a different species? Fascinating.