The Autofiller version of the twist filling fountain pen is simplistic. An ornate stick is mounted to the inside of a standard sac through a hole in the end of the sac. The stick is accessed via a blind cap and can freely rotate in either direction. To fill the pen, twist the rod to wring out the sac. When you release the rod, the sac twists back and expands, drawing in ink. There is no “stop” to prevent over-twisting. The blind cap/barrel end are seen in two forms. There is a more elegant version with the stick emerging from a narrow hole (the first pen pictured). In this version, there is a wide end of the rod inside the sac, and the rod is too wide to remove via the blind cap end of the barre. There is also a cruder version where the end of the barrel screws off revealing a barrel sized hole (pictured second). It is easy to see why the little stick for twisting is more easily lost from pens with the second type of blind cap. I have seen pens with the second deign with both the ornate carved stick as well as with a plain narrow rod for twisting, as shown.