The H2O Add-On Collar unit 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. This Add-On Collar can also replace a lost or damaged collar for all H2O 1800 and 1800 PLUS se Add-on or Replacement Collar/Receiver for the H2O 1810 PLUS, 1820 PLUS, or 1830 PLUS Lightweight waterproof collar and transmitter 16 levels of intensity, adjustable from the transmitter Built-in safety shut-off system Nick, continuous, vibration, and vibration and stimulation options
