The new release HD (Heaviest Duty) Ring is the toughest chew toy GoughNuts has ever produced. The HD rings are solid core for the absolute in maximum durability. Made from reinforced natural rubber and designed by engineers that make rubber for spaceships and aircraft. Like all Goughnut products, the HD rings come with a lifetime replacement warranty! GoughNuts are made in the USA and have set the standard for tough, durable chew toys.