Torrent Pitch Gauge is the easiest way to tell you impeller pitch. Impellers are supposed to be pitched to what you ordered but unfortunately are not. Check every impeller before installation, and make changes to your impellers pitch without buying expensive long lead time impellers. The only pitch gauge on the market that is for up to 165mm monster impellers and measures from 5 degrees to 30 degrees of pitch. One tool does it all. No need to buy multiple pitch gauges, this one does it all.