Features:

• At 1.9 cubic inches, it is by far the smallest you can buy
• Attaches to your dog's existing collar - (one inch width or less.) No need for your dog to wear a second collar
• Adjustable sensitivity levels so you can be sure to detect your dogs bark every time
• Uses loud but harmless audible sound to deter barking
• Lifetime Warranty
• Owners Manual

A well-timed tone can hush your puppy.
This remarkably light, one-ounce collar emits an unpleasant but harmless tone to correct your dog’s barking problem. The collar’s cutting-edge, bark-detection microphone can be adjusted to recognize your dog’s unique bark so that no other sound can set off the unit. This collar is most effective when used on small dogs.

The PetSafe Ultralight Sonic Bark Collar snaps right on to your pets existing collar so he doesn't have to wear a second one. The adjustable sensitivity levels allows you to customize it for your dog's unique bark. To deter barking, it emits a loud sound, similar to a smoke detector that startles your dog, disrupting his barking and discouraging him from continuing. While very effective, it is a perfectly harmless bark collar.