comments:
The wobble really bothered me also. The rings are a perfect fix, in my opinion. And the colour match is just a coincidence. You won't see it at all once it's inside. (I wrote instructions on how to assemble it in a couple of other comments.) https://www.amazon.com/dp/B0FXGCHGKJ
https://www.amazon.com/dp/B0FXGCHGKJ This is the one you want. The spring of the Rotring is loose in the pen, so take it out. Put the spring around the tip of the refill, and then the ring at the end. Then shove it back into the pen. The spring might eject the ring if you're not fast enough, but as long as you get it in there before that happens, there shouldn't be a problem.
I don't know about the spring replacement, but these are the rings people reference: https://www.amazon.com/dp/B0FXGCHGKJ
I strongly agree with this recommendation! That's exactly what I run in my Rotring 600. I don't like any tip wiggle or rattling noises when I write so I do use the o-ring hack to silence the pen and stop any wiggle. All gel refills are not created equal. This refill is super smooth and is my favorite Parker-Style refill. O-Rings