Battery free vibrating jewellery! Rattlebells consist of 6mm diameter balls with heavy metal spherical inserts imprisoned within the titanium casing. The encapsulated ball is three times heavier than the titanium shell and becomes agitated with the slightest motion, causing resonance throughout the barbell. The balls are permanently sealed and cannot fracture. Excellent for tongues, nipples and genitals. These barbells are internally threaded.