I use my bike quite a lot to commute in the city.
And, sometimes, to find the good street (believe me, in France, it’s not that easy) with the GPS while riding is tricky.
So I’ve been looking on the Internet to find THE good smartphone holder: unfortunately they are either bulky or expensive (and most of the time both)
Except this one: the Finn, a $9.95 silicone mount:
So let’s take the design on Inkscape:
Download the pdf file here and print it on a A4 paper sheet without scaling.
Cut the tube by cutting the paper pattern at the same time and remove the paper and tape.