Bell + Howell Ultrasonic Pest Repellers, 4 pack; Help repel pests, without the mess! Bell + Howell’s Ultrasonic Pest Repellers are unique devices that are designed to drive away ants, spiders, mice, rats and cockroaches only using ultrasonic sound waves. That means no unpleasant odors or dangerous chemicals to inhale and no messy, toxic sprays that may put your pet in danger. Every purchase comes with four Pest Repellers, so you can place them in multiple rooms throughout your home. So, say “bye bye” to unwanted visitors by using Bill + Howell’s unique Ultrasonic Pest Repellers!