Add another dog to your current SportDOG Brand® Rechargeable In-Ground Fence™ system (SDF-100C) or replace a Collar Receiver with the SDF-CR Add-A-Dog® collar. The Rechargeable In-Ground Fence system is expandable to any number of dogs over 8 pounds. The small, sleek Collar Receiver features a Li-Ion battery that charges in two hours and has a one to two-month battery life. Now featuring seven levels of static stimulation as well as vibration and tone, it's easier than ever to keep your dog safe and secure. Dependable in any environment, the collar features our DryTek technology - waterproof and submersible to 25 feet.