kink

It’s a constriction, just like a kink in a rubber hose, which means it can cause a serious reduction in the flow rate.

As long as there are no bubbles or kinks in the line, the free surface at each end of the tube will self-level.

You know, iron out any kinks or figure out if there's any issues with it, and then when it's a big deal in the iPhone 17 series later this year, should be all set.