Pen Ink Refill Guide

Refill formats look chaotic and are not. Fountain pens divide into standard international cartridges — short or long, used by a large share of makers — and a handful of proprietary shapes used by single brands. Ballpoints are dominated by the Parker-style G2 refill, which is roughly 98 mm long and fits far more pens than most owners realise. Rollerballs are the genuinely variable category, where length and tip profile change between makers and sometimes between models.

Pencils are simplest of all: the only numbers that matter are the lead diameter, which must match the pencil exactly, and the grade, which sets how dark and how smudge-prone the line is. Nothing else about a pencil constrains the refill.

The practical method beats any chart. Take the old refill out, measure its overall length and its widest diameter, note whether the tip end is a plain cone or has a visible step, and compare against the listing. Two minutes with a ruler settles what half an hour of searching by model name usually will not, and it is the only approach that works for older pens whose model names have long since disappeared.