Spring-loaded, twin pulley design mounts to derailleur hanger. Longer arm design allows for easy wheel removal. Offers proper chain tension on vertical-dropout frames when using the Rohloff Speedhub. . XC model has a longer arm for use as a Singlespeed chain tensioner. DH model has a shorter arm which brings the upper pulley closer to hub sprocket for better chain retention (shorter arm requires removal of tensioner to remove wheel). Designed to be used in conjunction with Rohloff's hub-mounted DH chain guide for optimal performanceItem Specifications: Color: Black, Model Name: XC/SS (0mm Offset), Weight: 115g,