The PERIMETER TECHNOLOGY – R21 Compatible Dog Collar is a reliable and comfortable way to keep your dog safe and secure. Made of conductive metal infused rubber, this collar provides significant protection against pressure necrosis, a condition which occurs when a dog either has a negative skin reaction to metal touching their skin or the collar is left on for a prolonged period of time. The easy-to-find collar features a patented three antenna design that ensures signal reception regardless of the pet’s orientation to the fence.