Let’s just say that you are the happy owner of an Omega Speedmaster Moon watch. Well, don’t you think you need the pen that goes very well with that watch? 
 
The Fisher Space Pen was approved by NASA in 1968 and hence was part of the equipment carried by the astronauts, when the reached the moon in 1969. But this pen was not only a revolutionary pen that worked flawlessly in zero gravity. It also helped the astronauts onboard Apollo 11 when the switch to the rocket engines broke.
 
With this said the reason to not buy this pen is none. Even if you do not own an Omega Speedmaster Moon.