Three hand blown, solid glass balls in graduated sizes- Ball sizes: 1.75" (4.5 cm), 1.25" (3 cm), 1" (2.5 cm). Balls are held together by ultra hygienic silicone strap which is removable for easy cleaning. Soft silicone spikes on strap for extra sensation. Glass and silicone become slick when lubricated. Both materials are durable, non-porous and phthalate free.