A Brief Introduction of Refills
The accessories of writing tools can be replaced many times.
A tube with ink or ink in the tube of a ballpoint pen, with a metal pen tip at the front and a writing ball embedded in the pen tip.
It also refers to the graphite bar (pencil lead) in a pencil.
The pen core is a rubber hose or suction hose in the pen tube.
Common neutral core pen head diameters are 0.5 mm, 0.7 mm, 0.38 mm, 0.35 mm, 0.3 mm, 0.25 mm.
Should be used properly, otherwise it will cause uneven oil production of the pen core and other issues.
The neutral core can be assembled with a miniature pen maker.