Here’s the patent for the usus.pi: WRITING IMPLEMENT FOR AN EXCHANGEABLE WRITING INSERT
Addendum: I’m not sure if this is really the patent for the usus.pi or – in other words – if the exact mechanism of that pen is covered by a patent. – Here’s another patent by Hilmar Nicolay: Writing instrument for writing or drawing has upper and lower parts of shell fixed in position relative to each other by magnetic force (I think this relates to the usus.i).
Do you have this pen? What does the action look like?
No, but it’s cheap on ebay. Assuming it follows the patent closely, it seems to be a hollow hemisphere (“toggle member”) connected to the lever. The refill has a cap with an inclined surface, onto which the hemisphere rolls and by that moves it downwards. The lever is moved past the dead center and thus remains in position.
Others that work similarly:
(Feel free to share more)
That is very cool, I might grab one
Wearever Flipit demonstration
(someone should make one from all metal)
There is one Usus Pi currently on Mercari.
At this point in time, it seems that all of the USUS writing instrument website domains that were previously live are no longer active. I figured USUS has completely discontinued writing instruments, if not their business altogether, but… they apparently have an Amazon.de store front, so… I guess that’s their sole place of business now? EXAMPLE
A seller from Spain back around 2024 had gotten a hold of quite a bit of USUS pen/pencil inventory and started selling it on eBay. I managed to get one… and had planned to get another, when inventory dried up. And then when he got some more, prices were quite a bit higher. Today there are people who no doubt bought from him and are now trying to flip them for up to 5x the original prices, which is ridiculous.
The USUS.Pi was the most interesting one to me, because of the lever mechanism. As a practical feature for something like a lead advancement mechanism, it would never be. But for the ballpoint, pretty usable. I have found that sometimes the mechanism fails to keep the spring compressed and it retracts. It has only happened a few times, but then “worked itself out.”
If USUS had continued producing more writing instrument models, my hope was that the “Pi” model would evolve. Maybe something contoured, so it’s not just a straight pipe (akin to the Platinum Z). One idea I kind of pondered for a bit was taking the shape of the LAMY Scribble, extending it by 1cm and putting the lever mechanism in place of the plunger.
It’s a shame that the USUS writing instruments are no longer available. The USUS website is still online, but their store is gone. By the way, the Amazon store you linked to isn’t part of USUS; it’s a media company that apparently sells other products as well.
The USUS.Pi is great, and I was lucky enough to get my hands on one about two years ago.
I just placed an order through this listing and it ended up being $83.45 after taxes, shipping, and currency conversion fees to ship it to Pennsylvania. It should take a couple of weeks to arrive.
I was curious, so I contacted USUS and learned that the USUS.Pi is still readily available. So there’s no need to go for bargains like this and that 
Yes I also asked them for a list and if they share one and give permission to share it, I will share it here.
Hey Gunther, when you say “readily available,” is that only through their Germany based website? I’ve not seen other venues, unless SEO isn’t being done on them (no Google hits).
We had a lucky streak of some rather nice pricing by an eBay seller from Spain. There wasn’t enough familiarity for the brand, so after a few people got theirs, prices came down due to lackluster bidding. I think I got mine for like $35 USD shipped. Someone else snagged one for just a paltry $17 USD before shipping. I wanted to pick up another USUS.Pi in another color, but supply ran out before I had the chance.
That’s how I understood it (I didn’t ask about international shipping). I think you can also order directly through the website by sending an email inquiry.
Thanks. I’m going to wait until after the US tariff debacle has finally been closed out.
Did anyone else hear back from them yet? I didn’t get an answer / full list of available pens..
Update: Basically after radio silence for a week I was rudely told I am not trustworthy. I just wanted to help (I don’t need one myself) because I like being helpful to the community, but I can’t do anything more sorry
Mine arrived. Initial mechanism review: very happy.
It does have a satisfying click sound.
But I wouldn’t recommend using it as a fidget device. There’s plastic bits in the mechanism that could wear out prematurely.
I completely agree. I tried to find info online about the internals or how the mechanism works but could not find anything.
Time to mill one open!
