Uni UMR-85 Gel Ink Pen Refill - 0.5 mm - Blue

This refill is usable in UMN-207 Micro, UMN-152, UMN-105, or UMN-138. I tried it in an UMN-138 pen body from Jet Pens and it works well. It writes smoothly; no flaws from what I can tell.