Review on BPA-RACING Motorcycle Chain Slack Adjuster Tool - Advanced Chain Tensioning Tool for Effortless, Rapid & Accurate Chain Slack Adjustment - Slack Setter Tool (Red) by Rich Rickenbaugh

I know a lot of people say this tool is not needed, but I disagree. I measured chain sag as usual and then applied and calibrated this tool. All I have to do now when I clean and lube my chain is tighten this to see if I'm up to spec. If not, adjust and center on the calibration mark. Another measurement is not required. If you don't trust a tool, double check with a tape measure to make sure it's working properly. I cleaned and oiled my chain yesterday and put this on to see if I need to adjust the chain. I was still absolutely certain of my destination and used a tape measure to check whether it was in the optimal position. Once you have full confidence in the tool, there is no need to do spot checks. You can always intentionally loosen or overtighten the chain and see if the tool makes a difference. This tool may not be necessary, but if you need to clean and oil frequently, it will save you time and keep you cleaner.