This is a laser cut tool so it is very accurate. I have started waxing my chain and from reading a ton of info from Zero Friction Cycling he recommends this as the most precise chain wear indicator to measure 0.5% wear. If you want to preserve your drivetrain as much as possible, then replacing the chain at 0.5% wear is the best way to do so and saves you tons of money long-term. Lots of other chain checkers are not laser cut and can severely underestimate chain wear so this is a good investment. I got this at a good price (~£17), but it is usually about double that, which seems very expensive, but it's an investment that will save you money long-term if you are serious about maintaining your expensive drivetrain.