These are Fisher Pen refills modified for use in the Valiant Concepts keychain pen or the Illumn Micro Pen. They are pressurized and will work in almost any environment as they do not rely on gravity for the ink flow.
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Pen Refills: Don't Throw Your Empty Pen Away—Refill It!
Pen Refills: Don't Throw Your Empty Pen Away—Refill It!