I need some help finding a few specific piece / fitting. This piece is a black plastic 3/4" threaded on one side and hollow all the way through. The opposite side of the threaded side is 1/4" opening. I need it to be a piece just like this that will screw into a black iron fitting, which this piece will. I need to be able to screw in piece from either side of the piece, meaning screw into a black iron fitting from the threaded sided of this piece or slide the narrow side in first through the black iron fitting and then screw in piece to iron fitting. I attached pics to help explain what I am talking about. Any help pointing me in the right direction would be appreciated. Thanks everyone.