I ordered a 160 100mm reducer. On the web page it said I would need a coupler to connect to a 160mm outlet, which I did. When the items arrived, the coupler and the 160mm end of the reducer were exactly the same size and so the coupler was no use. I called and discussed this with the customer services person who stated I had ordered the wrong coupler - I needed a female not a male coupler. I stated that the web site didn't mention that their were two different types, and in any case, why send a coupler that wouldn't fit the reducer? I have now ordered (at my cost) the correct coupler and hope this does the job. I am disappointed at this for obvious reasons. I would have accepted an FOC replacement.