Space Pen .375 Mag shell Casing The 375 Mag shell bullet A bullet pen with a difference, the rounded end shaped pen fits in side a genuine .375 Calibre MAG casing making it look like an actual bullet when closed. When the pen is open and the lid posted to the end of the MAG casing it makes an unique full length ballpoint pen. This pen is guaranteed to catch the attention of anybody. As the pen is made from brass it can be polished up to give a beauty shiny gold look or can be left in its rustic colouring to give it an authentic bullet colouring.