Reverse Colab Chain Tensioner Simple Just Got Better If you have a single-speed drivetrain, you'll need to keep tension on your chain to prevent it from falling off. The Reverse Colab Chain Tensioner is simple to use and ready for your next ride. The chain tensioner, in combination with Reverse's single-speed kit, means you can keep it simple, quiet, and hassle-free all season long. No more waiting at the bike shop while your friends are back on the chairlift for another lap. The chain tensioner screws into your rear derailleur hanger and the chain runs through the jockey wheels, providing a tight, smooth, secure setup. Features Quiet and reliable and even adjustable, too Chainline adjustment with the supplied washers Compatible with 9/10/11/12-speed chains and 13-17T sprockets | Reverse Components | Colab Chain Tensioner Black