From the manufacturer

The Colab Expert chain tensioner offers an extremely secure, robust, and easily adjustable chain tensioning system designed for freeride and downhill mountain biking. Combine with Expert Singlespeed sprockets and Sprocket Guides for the ultimate setup!

Features

• 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

Specifications

• Mount: Derailleur hanger
• Weight: 146g