The Ninja C is a two-part chain tool that fits inside the end of your handlebar
It’s designed primarily for skinny road bars, but the expandable bung allows you to fit it into a mountain bike bar, although we found it works best in thicker-walled carbon models.
The tool will split 11-speed chains, loosen stiff links, and there’s even a chain hook and storage for a Shimano chain rivet. Aluminium end caps sit flush to the bar, and protect the tool from damage and also stop dirt and water ingress.
At 50g, the Ninja C is lightweight, can be accessed when you need it and works pretty well as a chain tool, but you can buy Topeak’s excellent Link 11 chain tool for a fiver less. It won’t fit inside a handlebar, but it’s more robust, easier to use and no bigger.
Then again the Ninja can easily stay hidden in the bar until you need it to fix a chain, which, in our experience, is once in a blue moon.