The cSixx Cage is a bolt on solution to upgrade your Derailleur. CNC machined from a solid block of 6082 aluminum it offers a stiffer platform with more impact resistance. Tension+ is offered on certain models where possible, this allows you add additional spring tension, giving your derailleur a prolonged lifespan. We have added an additional 2 bolts enabling forces to be taken off the bearings, overall increase stiffness and makes for easier installation / servicing.