Universal twist ballpoint pen - able to use various gel/ballpoint refills

thingiverse

This pen utilizes a twist mechanism to extend or retract a gel or ballpoint pen refill. The twist mechanism can accommodate any refill with a length between 10cm and 12cm, and a diameter less than 0.65cm, such as the Fisher space pen, Parker ballpoint pen, or Pilot G2 refills. Insert the refill into the rear cap, securing it with 2cm of clear Scotch tape. Then screw the rear cap into the body. If the screw action feels too loose, apply some clear tape over the threads to increase friction. You can also use a small spring from an old ballpoint pen to keep the refill pressed against the rear cap. If you have big hands or are using a short refill and want a longer pen, insert a 2cm length toothpick into the rear cap before inserting the refill. Alternatively, edit the rear cap STL file in Microsoft 3D builder, splice the rear end, and attach it to the back to create a custom length. The visible screw provides a visual cue that the pen needs to be twisted to work. The 7S version features a body and rear cap with seven facets, preventing the pen from rolling off the table. Why seven? Google "number 7" to find out more!