The Fisher "Bullet" uses the original "Space Pen" refill used on all manned space flights. The original Fisher gas presurised ball pen refill allows you to write upside down or at any angle without the ink stopping flowing. The Fisher Space Pen is a must have item for anyone who writes on the go, Police, Couriers, Tradesmen or anyone who works 'out and about'. This item, with its PDA point for use on electronic organisers or Blackberries is the ideal functional pen!