The R4K is a completely new race collar for 2016. It features a revolutionary Koroyd™ core with superior impact absorption and a reinforced nylon upper shell. The chassis has been completely redesigned to be lighter and more aerodynamic. In an impact, the head is pushed down on the race collar. The R4K effectively fills the gap between your helmet and shoulder with Koroyd, which absorbs impact energy better than standard race collar materials.