"O"" so easy to use! Each cock ring is one size fits most made of soft silicone. The ring is designed with pleasure bumps for her and pleasure knobs for him. The vibrating bullet has an on and off switch with a battery included that will last up to 30 minutes. Once correctly positioned, it will give gentle stimulation to the penis that is then transferred to the partner during intercourse. This is a one-time vibration of fun."