This is not a shock collar! The Pettags No-Bark collar is a safe, humane and effective solution to help train dogs. The adjustable no-bark collar is like getting two collars in one. With two different modes to select from, the collar can be tailored specifically to your dog's needs. Sound mode releases a high frequency sound that deters dogs from barking. The vibration mode will vibrate every time the dog barks. - Two levels of stimulation (high and low). - No uncomfortable sensor probe. - Shower proof (not waterproof). - Adjustable nylon collar fits most dogs. - Battery Powered: 3 x LR44 1.5V battery cells (included). Sizes: Small fits dogs from 8 to 25 pounds.