I bought the 2 dog system, have only had it for 3 days now and I love, love, love it! I have a 120 lb. Mixed breed who is a wonderful dog but he loves to run. He was constantly running out when my back was turned and doing an hour or so round to the neighbors yards. We had the pet safe yard and park training collar with remote, so he was good when you were in the yard watching him. He knew his boundaries because he didn't want someone to shock him. The problem was when the doors were open and your back is turned he is gone in a flash. Real sneaky like too. He wouldn't make a sound. I had enuff and traded in the handheld unit for the wireless fence. He has had this collar on 2 days now and he has been zapped 3 times and returns to the yard right away. He has learned the flags r his limit in 2 days! Our property is very long and narrow, so I do wish there was a way to put the signal in an oval shape because he can go about 20 feet on either side into the neighbors yards. If I make the signal smaller to keep them out of the neighbors yard then he doesn't have hardly any room in our yard. My neighbors don't mind him in their yard some so this way I placed the flags on our property line so he has a visual of where he can go and if he crosses too far into their yard he gets zapped. He is content in his own yard now. We just got a puppy so I haven't really tried it on her. I put it on the beep only setting so she hears the beep when she gets too far, but she rarely does. She follows her big brother around for the most part. I just love that my dogs have the freedom they want and I don't have to worry if my doors r open where they are. Gives us both freedom! The only thing they could improve on is the batteries. They should make this collar rechargeable like their newest model wireless fence. I don't like the idea that I have to replace batteries that aren't cheap, although I have a good supply of them on hand just in case. I would have bought the updated model however I have a sloped yard and that model seems to have inconsistency with the signal on sloped land. Make rechargeable collars for this unit and you get 5 stars.It's is affective even for stubborn dogs . But the boundary changes so much it's hard to tell where it is .Works wonderfully... one thing. Make sure to it off while in the car. The car acts like a faraday cage and causes it to zap. Different than our old buried wire system...overall very pleased!Great product!It's perfect! Works great! Our German Shepherd can now run and play outside and she won't leave our yard. I just wish there was a rechargeable battery in the collar.