Sorry for lack of detail in first post.
The pen I am looking for is in essence a more durable, refillable version of the uni ball jetstream 101.
I like the pen a lot, as it is also good for maths as well as writing , unlike a fountain pen. However I am annoyed that it is not refillable, and I really just want a pen for life to stop constantly having to buy a new one every 3-4months.
Is it a gel pen?
Yep. I used multiple for school since the third grade (I’m finishing highschool now). While the pen is great, the refils are terrible. They sometimes dry from sitting for ~2 months and become hard and scratchy (most of my multicolor ones are like this). But the Pentel EnerGel refils fit in the g2 (but not vice versa).