The H2O 1850 Add-On Beeper collar is compatible with the H2O 1850 PLUS system and it can also replace any lost or damaged H2O 1850 or 1852 collar unit. All H2O 1800 PLUS series models has an 1800 yard (1 mile) range and comes with completely waterproof and rechargeable (Ni-MH batteries) transmitter and collar units. The transmitter has a No-Slip/Soft-Grip rubber coating and will actually FLOAT ON WATER! 16 levels of Nick and Continuous Stimulations come standard on every model in the H2O 1800 PLUS series line-up. Vibration feature is available in the H20 1820 PLUS. DT Systems Jump and Rise Stimulation features are found on the H2O 1830 PLUS. The H2O 1850 PLUS comes with a Beeper/Locator. The H2O 1810 PLUS H2O 1820 PLUS and H2O 1830 PLUS are expandable to a 2-dog or 3-dog system by adding H2O Add-On collar unit(s). The H2O 1850 PLUS is expandable to a 2-dog system by adding an H2O 1850 Add-On collar unit. Features: - Add-on or Replacement Collar/Receiver for the H2O 1850 and 1850PLUS - Lightweight waterproof collar and transmitter - 16 levels of intensity adjustable from the transmitter - Beeper with locate run and point and point only modes - Nick and continuous stimulations