Surface Pro 4 pen / stylet cap

thingiverse

A little stronger as the original source file : "Cap for the pen of the Surface Pro 3 & 4. This item will protect the vulnerable tip of your pen from breaking when it's not in use. There is a cut made on the cap so that it will be possible to stick magnetically the pen to the side of the Surface device while the cap is on. The top structure is designed in a way to be slightly flexible and slightly smaller than the pen. That is made specifically for the cap to expand when the pen is inserted and thus hold the pen with enough force to be secure and easy to remove."