Zebra F-Series Ballpoint Stainless Steel Pen Refill, Fine Point, 0.8mm, Black Ink, 2-Count

If you want an adult pen then here it is. I am a machinist (I work in industry) and this is the single best investment. The size is perfect, they are durable, the line size is small enough for the little boxes I have to fill out but it rolls smooth enough it doesn't rip paper. It doesn't bleed and you can buy ink refills.

I love this slim power tank refill. I use these in other pens that come with poor quality refills. I have a few packs of the full sized power tanks, but the refills are very thick. These are the only pens that work constantly in the welding shop.

Fit my Zebra pen as expected. Love this pen and glad I can get refills for it.

A very good pen refill. Smooth flow. Fast-drying ink.

I love this pen. Been using it for about a year now. Sturdy, we'll made, and a joy to write write with!