Cloud 9 Novelties Duo and Trio Borosilicate Glass Kegel Balls are perfectly weighted and encased in a silky smooth, premium silicone sleeve. These high quality hypoallergenic, smooth polished borosilicate glass kegel balls will help strengthen the pelvic floor muscle. Ideal for temperature play. Cloud 9 Novelties Health and Wellness Premium Borosilicate Glass Kegel Balls Recommended for Bladder Control and Pelvic Floor Exercises. Borosilicate glass is hypoallergenic, lead free, and BPA free. Premium Kegel balls work with your body's own motionFeatures a body safe, premium silicone tether cord. Weighted Borosilicate Kegel balls are easily removed for cleaning.