Anti Bark No Barking Tone Shock Control Training Collar For Small Medium Large Dog Pet "+" /"-" button, used to adjust the sensitivity to the bark(7 levels adjustable), the more sensitive, the easier to trigger the collar Adjustable Collar length from 9.84" to 28.74" to suit for different dogs: small, medium and large (Not for huge) Including test light, easy to test the functionality and sensitivity by blowing Can distinguish your dog's bark from other environmental noises and automatically delivers sound and shock after each bark. A 6V battery included