DT Systems H2O Plus Add On Training Receiver Collar: * Can be added to any existing H2O 1800 Plus series training system (excluding beeper models) to expand your unit up to a 3-dog system * Can also replace a lost or damaged collar for all H2O 1800 and 1800 Plus series systems (excluding beeper models) * Fast and simple programming into your system * Digital technology * Up to 1800 yd (1 mi) range * Lightweight and waterproof * MAXX-Range Internal Antenna System * Rechargeable Ni-MH batteries * Built-in safety shut off system * Includes 1 collar unit with a collar belt and a double-jack cable * Limited lifetime warranty