UltraSmart In-Ground Pet Fencing In-ground pet fencing system for dogs 6 months or older Audible and visual wire-break alarm, plus 24/7 battery backup Rechargeable waterproof receiver; collar fits neck sizes 8 to 24 inches Run-through prevention; 500 feet of wire included; expandable to 25 acres Measures 2-3/4 by 3/4 by 1-1/4 inches; limited lifetime warranty