Well it's exactly how the word sounds - rip stop.
It is very strong woven nylon fabric that is reinforced to prevent tearing.
During weaving, (thick) reinforcement threads are interwoven at regular intervals in a crosshatch pattern.
And we've done a lot of testing to make sure our shirts stand the test of time.
You can read more about the history of ripstop and how it's being used in outdoor recreational areas on the Propper website.