What makes up a pen – Europium Zone

Question: What makes up a pen
- Keywords:
  material,
  pen,
  technology
Asked by Ruby2005 to Kerry on 13 Nov 2014.
- Kerry O'Shea answered on 13 Nov 2014:
  
  A (ballpoint) pen is just a plastic tube filled with ink, with a small metal ball at the top to control the ink flow.

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