I have to report great disappointment with TWSBI customer service
My TWSBI 700R came with F nib. Then I separately ordered a M nib from LarryPost here in Sydney Australia which I finally wanted to install a couple of weeks ago (when I had some spare time). When I did I noticed the black shroud of the nib protruded down below the steel circular ring. So I queried TWSBI and asked if it could be replaced because my F did not have that problem. I was told to take it apart and send a photo and was then told there was nothing wrong with it and it must be my fault I did not assemble it correctly. I told TWSBI customer service the picture I sent was how it was when I received it. Also, now I reassembled it there was no change. After some more very unhelpful correspondence with implicit criticism of me I was then told to remove an O ring. I also pointed out that since reassembling it did not write as richly and was told that was also my fault.
Considering the original situation was not my fault, all in all, the TWSBI customer experience has proven to be repeatedly very disappointing in this case. So I would not recommend them considering my initial request for replacement was simple and was supported by recent sales receipts.