Using softer foam or hollowing out the inner circumference like other companies do still leaves the car feeling squirmy with a less accurate feeling through the bumps. Not to mention the loss of durability. Gil Losi and Mark Pavidis knew this compromise was not the solution. The solution they found was the addition of lateral grooves to the inner diameter. 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. No compromises. The result is a more predictable handling car without giving up durability.