The rear tire from my son's bycicle was getting flat with apparently no reason. I did try to repair it a few times but the solution didn't came until I installed one of these.The STL available to download is for the Schrader tire valve type. Hopefully, the OpenSCAD script can be used to generate caps for other valve types.This thing, as provided, requires a M3 bolt (10mm of thread or more) and corresponding nut, a couple of washers is recommended.The squared whole is for an optional zip tie to secure (loose) the cap with a spoke, we just want to prevent someone to try to unwind the cap.Warning(s)!*The required tools vary depending on the screw/bolt used (don't forget something to cut/remove the zip tie)