Phillips ultimately created a workable artificial foot made from carbon graphite, which was not used by any other company. Unlike all previous prostheses, it stored kinetic energy from the wearer's steps as potential energy, like a spring, allowing the wearer to run and jump as if they were legs. A prosthetic foot that he created to improve the functioning of athletes, the Flex-Foot Cheetah, is used by double-amputee and Paralympics gold-medalist Oscar Pistorius, and about 90 percent of Paralympics participants use a variation of the original Flex-Foot design as well as thousands of people around the world. Phillips sold Flex-Foot to Ossur in 2000, which continues to manufacture the artificial foot which many athletes to this day use in their sports.