We actually use this for our indoor cats to keep them from going out the doggie door. We tried an electronic dog door that latched after the dogs go through and did not unlach until the dog approached the door. The cats quickly learned that they could lay under the dog door and run out between the dogs' legs. This keeps the cats away form the door so they can't run out. We have found a second disc was necessary because they found if they run fast enough through the 10 ft field that it will not shock them. So we added a second disc so the field would be bigger and fool the cats into thinking they could not run through it. It has worked so far. One cat goes up to the field daily to see if it will beep at him. If he gets a beep he will back off. If there is no beep he will inch forward to keep testing it to see if he can get out. We have loosened theri collars so much that it will not shock them now. The beeping is enough to deter them now, because they think a shock will follow the beep. The other cat, we have removed his batteries everyonce in a while and he doesn't even bother to go near the door anymore. This works pretty good. We also used it to keep them out of a closet where they liked to pee.

Pros: The recievers are light and it works

Cons: I hate having to use it. I wish there were a better way.