Innotek Extra Receiver for SD-2100 and SD-2200 Systems Durable extra collar receiver with waterproof case Designed for SD-2100 or SD-2200 in-ground pet fencing systems Reflective collar strap and receiver; collar fits neck sizes 8 to 21 inches Contact probes; convenient test light; rechargeable battery Measures 1-7/8 by 1-2/7 by 1-1/6 inches; limited lifetime warranty