It’s very effective. Excessive barking is one bad behavior nearly all owners would want to correct. Please remember that it’s not as easy as pushing the trigger to stop them; there is a method to it. Most collars have training manuals in them, often detailing many types of training techniques. On the other hand, some collars have an automatic anti-bark function which makes them much easier to handle.
Make sure you show some love if they do behave to further cement good behavior.