The Minimo is among a class of pens that I don't lump in with the pocket pen class. The Minimo is even smaller — so much so that it's uncomfortable and difficult to use. But the main point of this pen is to stow in places other, more comfortable, pens just can't. I've tried a few of these pens and mechanical pencils in the past. They're generally billed as something you can slip into a small notebook, a wallet, pocketbook, or other small space for those "just in case" moments where you don't have another pen available. Ever seen the pen on a Victorinox knife? That's the level of minimal design we're talking about.
The Minimo is only 9 cm/3.56 inches, which is small enough to easily fit into a wallet or pocketbook. It's also only 3.6 mm in diameter, which is quite an accomplishment. This is barely large enough to allow space for the D1 refill and spring to fit inside the barrel. And, it even packs in a retractable mechanism and a nose cone that threads onto the tiny barrel. From an engineering standpoint, it's impressive that they were able to get the tolerances this tight. This pen feels solid and reliable. The retractable mechanism is similar to other larger pens that feature a switch on the upper side of the barrel (like the Tactile Turn Side Click). Depress the top to extend the refill, and press the tab to quickly retract. Operating the retracting mechanism is flawless, which I'm still impressed since it's all so small.