If you are unaware of the Retro 51 Tornado (review), it is one of my most recommended pens for people looking for a high quality, great looking, affordable pen. It fits a need in the $20 price range for people wanting to treat themselves or give a gift to others. I love it too, but there is one thing that has held it back ever so slightly in my personal rankings - the refill is too wide.
The Tornado ships with a Retro 51 branded Schmidt 8127 roller ball refill, which has an 0.7 mm tip. In the search for a finer tip, Schmidt's own 8126 model and its 0.6 mm tip has been the most recommended replacement. I finally received a couple now that JetPens is stocking them and I couldnt be happier.
I did a simple writing sample above and the difference is clear. For those of you wanting a finer refill for your Tornado that has the same qualities as the stock refill the Schmidt 8126 is the answer.