Product review (5 stars): Just what we needed!
Ahhh!  Thank goodness we found this part!  Moved into a new house and the washer had a terrible moldy stink.  Got the smell out with some cleaning products and this little piece (that must have broken off and been lost by the previous owners) has been a god send.  It allows the air to circulate between washes and the nasty smell has not come back.