Adjustable cartridge pen housing

A pen comprising:

• a pen comprising:
• housing having a distal portion and a proximal portion threaded together;
• a cartridge disposed within the housing;
• an adjustable control element disposed within said proximate portion of said housing to accommodate cartridges of varying size
• wherein said cartridges abuts against said control element;
• and
• wherein the threading and unthreading of the distal portion and the proximate portion causes the retraction and extension of the cartridge.

A pen housing comprising:

• a pen tip;
• a pen grip;
• a pen barrel;
• and an end cap accommodating a cartridge, wherein said pen grip and said pen barrel are threaded together;
• said cartridge having a writing tip end and a butt end;
• a set screw threadably attached within said pen barrel to move cartridge distally and proximally to accommodate varying cartridge lengths;
• wherein the butt end of said cartridges abuts against said set screw;
• and
• wherein the threading and unthreading of said pen grip and said pen barrel causes the retraction and extension of the cartridge.

A writing instrument comprising:

• a housing comprising;
• a pen grip;
• a pen barrel;
• a control element having a threaded end and a pin end;
• a cartridge having a butt end and a tip end;
• wherein the pin end of said control element abuts to a butt end of said cartridge and
• wherein a threading and unthreading of the pen grip and the pen barrel causes the retraction and extension of the cartridge.