This product is the ball body , volume size is indeed according to the structure of the human body but designs that, accord with human body study of meritorious service completely , dodge to press close to personalization more when moving round, be comfortable , free intention more when being put into use. Originally, the product gets through ceaseless inkstone hair many years , test , ameliorate, create disregarding going ahead being to fit all on package , exterior , functionality, structure , security and comfortableness. Shock time above 50 minutes, crown of being the same kind product.