The purpose of the K.1 Silicone Magnetic Balls is to provide the most flexible and fun way to do pelvic floor and vaginal strength exercises. Small enough for everyone to insert with ease, they combine to provide a larger shape within that you may squeeze your PC-muscle around. Weighted sufficiently, the balls do drop to the vagina opening with ease and can be taken out one ball at a time. The 2 smaller, black balls are magnetic and the 2 larger, pink balls are not.