D.T. Systems H2O ADDON-O Orange Receiver Collar Up to one mile range; lightweight, waterproof collar Maxx-range internal antenna system in collar belt Rechargeable nimh battery system; built in safety shut-off system for improved battery life and reduced cost of operation Blaze orange collar 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