This one is a no-brainer. The Park CC-3 Chain Wear Indicator could be the perfect tool. it’s so helpful, affordable and easy to use that it belongs in every roadie’s tool box — even if it’s the only thing in there because you’re so mechanically disinclined.
You won’t have any trouble mastering the CC-3. Just hook the curved end inside a link with the 0.75% scale on the bottom edge. Lower the tool to the chain. If the flange doesn’t drop in, keep smiling and go for a ride. The chain is practically as good as new.
The CC-3 is 5 inches (13 cm) long. It works on any bicycle chain, according to Park Tool. it’s made of laser-cut steel for precision and durability. It doesn’t seem likely to wear or be damaged by a lifetime of use.
Nice touch: When you flip to tool over to try the opposite scale, the lettering and number are still right-side up.