The Keeper does what is says on the box, it keeps the chain on. It is a simple idea for those who want to run a single ring. Compatible with the 31.8 and 34.9 mm seat tube standards would be the perfect match for those who rock one ring in the front and many gears in the back of their bikes.
Seat tube diam.: 31.8mm/34.9mm. Weight: 44g.