The PetSafe Happy Ride Metal Dog Barrier is suitable for larger dogs, but a small to medium dog may be able to work its way under the bottom or along the sides, depending on how determined they are. My 50 pound hound had no problem slipping underneath and dislodging the barrier from its vertical support pads. But that was the first use. After adjusting the spacing and the tension pressure, the barrier held. I like it because it is well engineered and extremely adjustable. For the money (my purchase was 40% less than the retail price), nothing else out there compares with it. The assembly instructions were spot on and it's obvious that the entire item is well thought out.