Pens with a tip made of a very small cylindrical tube with one open end making contact with the writing surface and generally with the other end in contact with the ink supply (alternatively they may be dip pens). They are used primarily in recording instruments, but also for writing and drawing. They are distinguished from the many other types of pens that work via a tube and capillary action in that they do not have a ball point, felt tip, needle, or other object fitted into the tube of the writing tip, but instead use the small diameter of the tube and external air pressure to regulate the flow of ink.
