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.
Specialized tool to fit 12-spline lockring. I found it helpful to hold it in place by re-inserting quick release skewer before wrenching to keep it from slipping out.
Crank puller that does exactly what it is intended to do. I travel with my tandem bicycle and I use this crank puller to remove the cranks as part of the bicycle disassembly and packing process.