Silver Balls In Presentation Box are Ben Wa style balls. Multiple use weighted balls can be used in conjunction with Kegel exercises. Balls do not vibrate with batteries but rather with kinetic energy. Use for pelvic exercise by holding them in to strengthen muscles. Safe and pure for body and pleasure. Made using phthalate free, non-toxic materials Balls steel with plating, ABS plastic presentation case. Each ball measures 1.6 inches in diameter. Always clean before and after use plus between partners.