For years, I'd tried every tool I had to stop the chainring nuts from slipping when tightening, but nothing worked. This tool does the job and is cheap. If you don't have one, pick one up before you need it.
Park Tool has been making quality tools for a long time. I need this bottom bracket tool in my collection because I'm changing my cranksets several times a year. I have a front double, single and triple I switch in and out for mountain biking, cyclocrossgravel and road style riding. If you like to work on your own bike instead of taking it to your LBS, then this bottom bracket tool pays for itself in probably one use. You can count on the quality of Park Tools.
This kit has almost everything you need to keep your bike in optimal tune. I have campy components on some of my bikes, and there are a few specialty tools that this doesn't include, but for must stuff, it has everything needed. If you are looking for a nice set of maintenance tools, this is a worthwhile investment.