I live on a one and a half acre block, I owned two very large mastiffs that routinely escaped over my fence so I heigthen my fence to 7ft all the way around an epic undertaking but solved that issue. However when I got my two new dogs a Neo Mastiff and a Band dog I thought I was OK, but the one dog was determined to get out so much so she dug under the fence, I would fix it and she would dig under somewhere else.. I couldn't keep up. I had tried radio fence/collars before (off ebay and other online stores) but they were useless, they would zapp at random times causing the dogs pain when they weren't doing anything wrong, I found out that the transformer outside the boundary would make it false discharge, trucks going past would cause it to discharge, it was so frustrating that i binned them. I was reluctant to go back to a dog fence/collar set up but after looking into dogline and seeing they had a fixed fm frequency that wouldn't be interrupted by outside transmissions I took a punt. 3 years on and I haven't had a single issue. The collars work as expected, they are robust and the battery life is amazing. There customer service is second to none as well if you need replacement parts (batteries, line, collars etc) They get 5 stars from me.. Cheers Matt