The Sure-Grip Rollout Wheel hit the market like a wrecking ball! This wheel is made with the same urethane formula as the Sure-Grip Zombie. Sure-Grip has found a pouring method that eliminates inconsistencies in wheels. They use this method in higher end wheels, like the Rollouts. Their hollow core technolgy has been modified with a glass filled hollow core making it stronger, while providing enough give for that great grip we are all used to from Sure-Grip!