The purpose of making this simple two-piece bolt-style pen is to fit most of the pens in your home.

You need the following materials:

• A M3x6mm bolt
• A pen with a diameter of 2.85mm
• A spring from a push-button ballpoint pen

I suggest you print the model first, and then cut it according to the size.

Moreover, if your spring feels too hard, you can cut off one end; if it's too short, you can stretch it to make it softer.