These love balls are designed to strengthen pelvic muscles effectively, and you can use one ball or two depending on your strength level. These pelvic training balls oscillate for maximum impact. These love balls are easily cleaned and maintained. They're made from a high quality silicone that's free from phthalates for safe regular play. The pink balls are weighted for extra intensity and you can use one as a beginner, and progress to two balls to suit your pace. These pelvic training balls are smooth and comfortable. They're waterproof for even more versatility.