We have 6 month old golden retriever and a fenced back yard. Our golden began digging under the modular that we live in and no matter what we tried to do to block her she still dug around it, through it, in a new spot etc. The fence was doing it's job already so our alternatives were to build a concrete kennel/run for her, stake her out, or put the invisible fence to work. When I ran accross this wireless invisible fence system, I saw this as a great alternative to the previuos mentioned fixes. We got it in two days and were ready to try it out. We followed all the instructions to get the perimeter set-up (which is an adjustable sized circle)and got down to training. The manufacturer has a month or more training schedule - our golden caught on quickly in just two days (we spent about 6 hours training in total.) We followed the instructions to a tee just at a more rapid pace since she began catching on after just one shock at a level 2. We left the flag markers in place for about 8-10 days and began removing them as directed over three days. By this time the dog (Holly) was used to hearing the beep and knew what would come next if she continued in that direction. It has been wonderful , as this also keeps her from wandering off to the neighbors, out to the road, or disappearing out of shouting range. The adjustable radius is great for containing Holly in a smaller area, such as at a BBQ, away from the pool, kids, etc. This is not a system for a small dog as the collar is bulky - I would say the dog should be at least 25 lbs to support the collar. The system is expandable if you buy additional collars (which is still a lot cheaper then building a fence or concrete run). I can't wait to take it camping with us so Holly can roam freely in her area and not need to be staked down or shut up in the car or trailer. The only down side to this system is that the central unit is not weather proof - so you are advised to place it indoors. This was not an issue for us as we have shop and a pump house, but I can see for some if you only wanted to contain the dog in the back of the house it might pose a problem since the circle size might need to be reduced. The only improvement I can suggest would be to make the unit smaller (it is about the size of a gallon jug) and weather proof, so you could place it in a tree or on a table to get the containment area exactly where you want it (guess you could use the old wire system to do this as well). Overall though it is a great invention works well for Holly and we don't have any more digging under the house.FYI - for those that think the shock is cruel - I held the collar in my hand and it is not painful, but I can feel it (it is much like the sensation of placing your tongue on a 9 volt battery - not painful)- I think since it is a different sensation dogs react to it. We have kept the level at a 2 for Holly (it goes up to 6, which I would imagine feels like a zap, bnut just like humans some dogs are more or less sensative then others)- but I have only seen her get shocked 4 times, 2 of which I made happen in order to train her to go back inside the circle instead of outside it and 2 of her own mistakes. Holly responds to the sound now and eventually she won't even need the collar on to stay within her boundary.One year later - still works. Holly (the dog) definately knows where she can roam when the collar is on. We have replaced the battery 5 times, so about every 2 months. There is a low battery indicator on the collar itself and the batteries are pretty cheap here on amazon. We leave the unit on 24-7 becasue it is just easier than worring about openeing a door and having Holly escape without her collar and we have not had any issues. Holly actually wants the collar on, after a bath she goes straight to where the collar is and can't wait for us to put it back on. After the inital training Holly only has gotten zapped one other time and she was chasing a duck - this was about 7 months after being with the collar - she did escape her boundaries although she returned back inside the boundary as well - she is almost full grown so we figured the level 2 was just not as effective as it had been when she was a pup. That same afternoon we upped the level and let Holly test it again, now that she thought she could get outside the boundary area. It worked, she cried out, so we knew she felt it, she immeadiatly returned to the front porch and still to this day if she hears the warning beep she returns straight to the front porch to ensure she does not get zapped again. The Collar is still in good shape and we hope the unit last another couple years.