My new rollerball pen (from another vendor) just didn’t write like my others; it would often skip and occasionally smudge. I think it had just been on the shelf too long and the cartridge had dried out. So I ordered a popular gel refill (in F), but to my dismay it behaved like a ballpoint- too much feedback and requiring vertical pressure to get an even line. Brought my pen to Wonder Pens, and they recommended this Schmidt refill (in M). *This* is what a rollerball is meant to be - wet and smooth, glides across the page with no pressure and no skipping. This will be my refill going forward.
