Family-security via Amazon offers the Fredi Pest Ultrasonic Repeller 6-Pack for $25.99. Coupon code "HO38Q9PD" cuts that to $18.19. With free shipping, that's $8 off and the best price we could find. It features a 22KHz to 65KHZ ultrasonic frequency range and 1,200 square feet of coverage per device. Deal ends May 31.