If you have an older model Zebra F-701 pen then you might have realized that the pen is almost entirely metal, but there is one prominent plastic part. Meanwhile the cheaper Zebra F-402 uses a metal component for the single piece where the F-701 does not! This video explains how to combine the two into a fantastic sub-$15 EDC pen.
2019 Zebra Pen Update
A lot has changed since this video was released!
First of all, the Zebra F-xmd has been released. This is a full-metal version of the F-701 that isn’t aimed at the US markets, but it’s easy enough to get one here.
More importantly, at least for people in the United States, the F-701 was relaunched in April 2018 as the “All Steel” F-701. The plastic component around the knock button was replaced with a full-metal one. On their website Zebra says:
The STEEL F-701 is now all metal from tip to clip, featuring a metal ring and refill.
Exactly what we always wanted!
So yes, this hack still works on older models, but if you are open to the idea of buying a new pen, then there is no need.