Pull straps to snug or loosen on nipples. Squeeze me till it hurts. Features Easy push button vibration.Waterproof. Phthalates free. RoHS compliant. Materials: Back is silicone. Chrome is ABS. Size: Overall length: 4.25 inch. Width: 1.5inch. Diameter: 0.75 inch. 1 AAA battery each vibrator (not included).