Feature(may vary by option.)

●This is heat sensitive erasable Ink cartridge, fit for erasable fountain pen with 3.4mm bore diameter, such as OASO K019 fountain pen (ASIN: B0CR5ZDQHP).
●Cartridge Lenght:51mm; Cartridge Diameter:5-8mm; Bore Diameter:3.4mm.
●There are 4 packs, 6pcs per pack, 24pcs ink cartridges in total.
●Please remove old Ink cartridge first, then stab the small part of the ink cartridge to the pen body (you will feel and hear a "click" which means the cartridge installed in right place), and please wait a minute for let the ink flow to the nib. If did not work, please change one other ink cartridge to try again.
●If any troubles about our pens, please feel free to contact us, we are glad to solve any problems with you.

[Blue (Heat Sensitive Erasable Ink)]

[Blue Black (Normal Ink)]

[Black (Heat Sensitive Erasable Ink)]

[Blue Black (Heat Sensitive Erasable Ink)]

[Blue (Normal Ink)]

[Black (Normal Ink)]

Description

We are the professional pen store, you also can find the other great pens in my shop.