- Replaces rear derailleur with chain tensioner for a simple, secure drivetrain - Expert version elevates the Colab chain tensioner for the most extreme use and easy adjustment - Adding 15mm of adjustability for the chainline by loosening one bolt, the Expert version helps riders achieve perfect chain alignment without the removal of the tensioner - Adjustable limit stopper as well as a pinch bolt on the mounting bracket and higher spring tension provide more chain retention and also maintains position when the rear wheel is removed - Compatible with 9/10/11-speed chains, 13-17 tooth cogs - Aluminum construction, made in Germany