The very nature of air tools has them "living" in environments with
dust and grit. To keep dirt out of the leader hose on my air tools I
cap them with baby bottle nipples on the quick disconnet fitting.
They are a good fit. . If you know someone raising an infant the
price and be really right as they need to be replaced, but they are
still good for my purposes. After a while they do get brittle and
they no longer work for my purposes, but I usually lose them before
that.

Perhaps there is a reason this isn't a good idea. I would be please
to hear you ideas.
Robin