This system is secure and effective for all hard-to-train pets. The PetSafe In-Ground Radio Fence has been proven secure, comfortable, and successful for hard-to-train pets over 8 pounds. The system works delivering mild static adjustment through two contacts points on a receiver collar your pooch wears on his neck. You'll need to install an underground fence by burying the included boundary wire and flags. Your pet is allowed to openly wander inside a safe area that you establish.