This is an option called the E-Z Slide, and it offers more mobility over the standard tether sliding system included with the R3 Rage. It attaches to the helmet to the D Ring Kit included with all the Head and Neck restraint systems we sell. It is available in different lengths, and is usually purchased after a customer receives his restraint and adjusts. Once the original tether is adjusted, you can measure for the E-Z Slide by measuring your original tether from end to end of the webbing, with the tether laid flat. This measurement minus 2″ will give the same head movement while providing freedom to turn your head. Most popular sizes for this is 14″ for the majority of customers fitted for this option.