So, for whatever reason tonight I decided to see if the refill from the Jetstream RT would fit into the barrel of my Uniball 207 Premier. I love the super-cushy grip of the 207 Premier, and it is a nice-writing pen. However, I still prefer a ballpoint pen over a gel or rollerball most of the time. I know, I'm weird. Most people prefer the gels and rollers.
At any rate, it fits. The Jetstream refill itself is a bit narrower, thus, the 207 refill does NOT fit inside the Jetstream body. But because the Jetstream refills have that wider ring at the end, it gives the spring something solid to fit against and makes it fit quite nicely into the 207 Premier body. I'm stoked. The JetStream sport is a favorite pen of mine because of the way the grip fits my hand nicely. They are nearly impossible to find locally however and when I can find them, I can only get the 1.0 mm. I prefer the 0.7 mm, which leaves me having to order them from Jetpens, which is fine, but I don't order much online and prefer to shop locally when I can. At any rate, the Jetstream RT isn't as comfortable for me to hold. Now I can just take the refills out of them and stick them in the 207 premiers! :)
It's so easy to make me happy.