Lamy ballpoint pen refill, M21 black
Lamy M21 ballpoint pen refill in black waterproof ink for all Lamy multi-system pens: 2000 multi-colour ballpoint pen, accent 4pens, cp1 and st tri-pens and cp1, st and logo twin pens. It's also the refill for the ultra-slim Lamy spirit ballpoint (now discontinued).
This matchstick-sized refill often fits other makes of multi-system pen too.
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Writing system: Refill