In more detail:
Gil Losi Jr and Mark Pavidis didnt want to use a softer material or hollow out the inner circumference of the insert so they have incorporated lateral grooves to the internal diameter of AKA's closed cell inserts. The lateral grooves allow the insert to flex vertically to absorb the large impacts while still maintaining lateral stability and overall durability AKA inserts are known for. The result is a more predictable handling car in the harshest track conditions. A stiff wheel combined with a laterally stable, vertically compliant insert equals faster lap times as Cody King proved when he used these inserts along with the new Evo wheel to take home the win at the 2010 IFMAR world championships.