E-best&reg; Rechargeable Auto Bark Device, Advance Bark Control Collar Humane uses painless tone followed by shock only if barking persists! Please note that the button is not for adjusting the volume. The turn button is for adjusting the sensibility of the collar. The led light on the device will light up if the dog barks loud enough. The additional light in the package is for testing the power of the battery. Small and Lightweight, effective on dogs from 5 pounds to 150 pounds! Operates on a standard 6 volt battery (INCLUDED) Length: up to 45cm