All brass & steel construction, variety of colors and finishes & tungsten carbide ballpoint tip The 400 series bullet space pen is the original Fisher ball point pen & most popular Fisher pen sold Pressurized thixotropic ink cartridges are hermetically sealed & write 3x longer than ballpoint pens Reliably performs in extreme temperatures (-30F to +250F), underwater, in zero gravity, at any angle Precision assembled & hand-tested with a lifetime guarantee against all manufacturing defects